At the price these guys are currently going at, I think there are few better values around. I did a lot of research before buying, and going by the impressions many folk have posted, one would think these sound massively different to the original Momentums. This is not the case at all - I owned both at the same time, and unlike most who have posted comparisons, I had the on-ears first. Compared to anything else, you can tell these come from the same family - indeed they should share an essentially identical 40mm driver that's simply tuned differently.

I find the on ear as comfortable as the over-ears, if not more so. The alcantara pads are super soft, and only get softer with use. Clamping force is a little high out of the box, but that's a super easy fix with a little stretching or simple breaking-in. The pads on the over-ears are often too small for users, something you don't have to worry about with the on-ears. I have no issues wearing them for hours on end, and their small size even makes it easy to lie in bed while listening to some music with them. They're also very easy to wear around the neck and the lighter weight makes them less likely to mess up your hair.
 
Isolation is subpar on these though. I don't generally want too much isolation because I like being somewhat aware of my surroundings, but you can hardly tell there's any difference when you have them on - isolation is very subtle. That said, once you have some music playing, even at low volumes, it's not that bad. A bigger concern for me is that these seem to leak more than your average closed headphone - not ideal for listening at moderate volumes in quiet places.
 
As for sound - they captivated me right away, but the bass definitely sounded bloated and slow. It's worth noting that I bought mine used. Like new, but still used, so I don't know how much they'd already been burned in. That said, it still took several days of listening to music to get them to sound their best - there was a noticeable difference in the quality of the bass after extended use. I'd assume this is because of a combination of the usual dynamic driver burn in, as well as breaking in the pad and metal band to achieve a proper level of clamping force. Definitely don't allow first impressions to sway you if you don't like them immediately. 
 
Once broken in the bass is quite wonderful. I find low end response on the original momentums to be a bit boring.This is not for a lack of quantity - the VSONIC GR07 Classic has less bass but is more engaging. It just feels a little soft, and slow. Too gentle. This is not the case with the on ear. The bass hits hard and fast, and extends easily into the sub-bass. 
 
The mids came as a huge surprise to me. I expected them to sound distanced and recessed and bloated by the bass, but didn't find this to be true at all. Listening to the over ear and on ear back and forth with the same tracks, there is hardly a difference between the two. The originals are a tiny bit more forward, but that's it. I actually think I prefer the texture on these too - cellos sound better with the on-ears to me.
 
The highs are the one area the on-ear noticeably lose to the over ear. Overall treble amounts are very, very similar between the two, but the over ear seems to eek out just a little more detail. Cymbals sound more realistic on the over-ears, for instance.
 
As for soundstage and presentation, the on-ears excel here too. Soundstage width is just as good as on the over-ears, perhaps even a little better. They lack a little depth and height compared to the over ears, but then compensate for this by having clearer positioning and separation. Instruments blend into one another more on the over ears than on-ears, where I feel I'm able to tell where everything is just a little more easily, particularly in congested tracks. This is made all the more impressive by the fact that the on-ears are, well, on-ears. I suspect this has to do a bit with the sound leakage and weak isolation.
 
The on ears have often been described as only really being good for bass heavy modern music, but I completely disagree. There isn't a single genre of music I've listened to that sounds bad with the on-ears, whereas I find myself a bit bored with EDM and some hip hop tunes on the originals. I get surprising enjoyment out of classical with these. Perhaps that's because I'm partial to making cellos sound good, something I find these do superbly well. But it's also because of their great instrument separation and texture.

On sensitivity and amping, both of these need a little more power than you'd think from 18ohms headphones to get particularly loud. When I'm on the go, I find myself often having to crank both Momentums to max volume - something worsened by the lack of isolation on the smaller model. As for amping, I thought the larger Momentum would take a clear lead when they were powered up, but I found the opposite to be true - the bass becomes tighter and more textured, and the treble improved to a point where it became difficult to tell if the over-ears were actually performing better than the on ears 

One final note: both of these sound better when you use the cable without the microphone. I've never been much of a believer in the power of cables... but it was noticeable here. It's not a huge difference, and it's less pronounced on the over-ear, but notes are more defined, with better instrument separation and overall clarity improvements. That said, the microphones themselves sound clear on a call.

I've spent two weeks with both the on-ear and over-ear, and I still can't decide which one I want to keep. Truth is, I'd probably keep the on-ear for sure if it weren't for the fact the over-ears isolate better and leak less. But on sound alone, there isn't a clear victor. What is clear, however, is that the on-ear are the better value, especially now that they can be purchased refurbished for about $100. 

These headphones cost $50 bucks yet they can take on the likes of the Denon D1100 and ATH-M50 with ease. They need a good amount of burn-in(200 or so hours) before they reach their full potential but they sound great out of the box. The bass reaches down past 20hz and punches with authority while being textured and tight, the mids are exquisite, and the highs are superbly detailed.

This is all presented in a soundstage that is wide and has rather impeccable imaging. The sound is the most transparent I've heard extensively(the previous best being the M50).

The build is not flashy or extraordinary, but satisfactory enough to make me feel like they will last years. They are semi open, but don't leak much more than some closed headphones such as the RX700 or Dre Beats.

I can't think of a better value in headphones than these or their very similar cousin, the Superlux 668B.

Full review at: http://www.head-fi.org/forum/thread/546544/samson-sr850-superlux-oem-review-a-50-budget-champion

These headphones are very unique, both in construction and sound. They are built of Cubic Zirconium, making them extremely durable, and have detachable cables. A jogger literally ran over mine, on concrete, and they aren't even scratched. The finish changes color from a gunmetal grayish color, to a bluegreenish hue in bright light. The cables, though having a slight memory character, are very thick and sturdy feeling, although they can add a bit of uncomfortable weight to already hefty earphones. Nevertheless, I've never had an issue wearing these cord up or down so long as I have a proper fit. They are shallow insertion, and comfortable enough to sleep with. Most earbuds/IEMs tend to die through cable failure, since they are constantly being put into stress because of their portablility, so it is a huge relief to see these have detachable cables which are compatible with Sleek Audio cables. One of my dogs chewed through the original cables(which miraculously still work most of the time, but sometimes the sound cuts out), so I was glad I was able to pay 15 dollars for new cables instead of 100+ for new earphones. However, they do suffer from one issue where the thin nozzle filters seem to fall off when doing a lot of tip changing, which pretty much 90% of head-fi IEM users do. This is not a big deal though, as many prefer having them off, and the issue is easily managable by taking a tiny piece of thin foam from some cheap earbuds and placing them into the nozzle(which also lets you comfortably modify the treble to your own liking)
 
Soundwise, the first thing to note is that these aren't for everyone. They are by no means neutral; but this doesn't mean they don't sound natural. Whether they do or not will depend on your ears and preferences. I am, fortunately, one of the many to whom these seem to sound very "natural", what with it's U-shaped sound signature presenting clear highs and (very) punchy lows. These extend powerfully all the way down to 20hz, while presenting a surprising amount of detail in the treble. Detail which rivals that of many balanced armature IEMs, by several accounts.  Though they have a pleasant decay at the bottom for realistic bass, they maintain necessary speed throughout the sound signature to provide ample detail in all the frequencies. Textured bass, clean mids, and detailed highs.
 
Though their soundstage isn't the widest, they seem to give the illusion of a large soundstage because of how transparent the sound is, and how realistic the timbre is. Separation and imaging/position is truly great, especially for a dynamic. One would think the Cubic Zirconium is just marketing, but not only does it provide these with outstanding durability, but also really reduces resonance to less than any HP I've heard. It's as if my brain feels that the sound emerging from these is so realistic, it artificially expands the soundstage so that it feels larger than any of my full size headphones. It is an intimate presentation that is able to expand accordingly to the music's demands. As a fellow head-fi member once described, their sound is seemingly "holographic".
 
I must emphasize again, however, that they simply aren't for everyone, but such is the case with pretty much every headphone. What make these headphones great for some may be what makes them lackluster for others, and viceversa. For those who need something with pristine detail to bring out the nuances in classical music, but still want the bass to get you moving through your Hip-Hop tracks, these are a great candidate. I bought them when they were available for 109 dollars earlier in the year. At 120, they are still an amazing value.