I did a side by side comparison of the 888s, MX-500s, and KSC-35s out of my Sony MZ-E900, MDLP 2 recordings, just to refreshen my memory. Here's my findings:
MX-500s overall had the smoothest sound, as in nothing sounded out of place. It has a bit of a warmer lower midrange than the 888s.
888s had the best transparency...using it I could very clearly hear the shortcomings of MDLP 2 (although, I can still plainly hear that swirly sound in vocals that you get with low bitrate MP3s with any of these 'phones, just that the 888s present that problem the clearest). However the 888s had a boxiness/hollowness to the upper midbass. Sensitivity is awesome on the 888s...it remains a good 3-4 levels below the other 'phones. Upper midrange was clearer than the MX-500s. This was with my LP pair of 888s (More notes below).
KSC-35s had the best impacting bass. In fact it's the only one that has any bass...the other 'phones have that phenomenon of bass you can hear but can't feel. However I found its lower midrange/midrange level to sound grainy, whereas it was smooth on the above earbuds.
Treble response was absolutely horrible on all of the above, I can't even begin to comment on it.
If I had to pick one I'd say the 888s had perhaps the most extended treble, as in you can actually hear some treble, but otherwise, all of the above 'phones had a pretty muffled sounding treble.
I did learn something very interesting out of all this. I have two pairs of 888s...a SP and a LP version, and I've owned and used the LP longer than the SP. Well in a side by side comparsion, the two 888s distinctly sound different from each other. The SP, which gets less use, sounded a tad thinner and had better treble detail than the LP 888s. It also doesn't have that hollow bass that I heard with the LP 888s. On the other hand, the LP 888s had a much wider soundstage, and it was also much more sensitive than the SP 888s. When I switched from the SP to LP, I immediately had to crank the E900 down two notches in volume because it was too loud. The only explanation I have for this is the SP 888s aren't yet fully burned in (I've probably put them on less than 30 times and I've had them for a year now), while the LP 888s are 100% burned in. If this is the case, 888s sound their best when they're about 30-50% burned in...once they hit 100%, that's when they start to get that hollow bass and to some, an overkill in midrange.
In connection to another favorite 'phone around here, those "treasured" 484s, it seems Sony just simply has a problem with hollow bass with all their earphones, exception being the EX70s. The first thing I picked up with I heard the 484s was how the bass sounded hollow. It looks like the 888s follow suit unfortunately.
I'd have to say now that my new favorite portable 'phones would have to be the MX-500s, regardless of price...because of the combination of easy on/off, size, durability, and price. I won't have a heart attack if I end up mangling the MX500s in my backpack, they sound as good or better than the 888s, and they're easy to take out and put on, and just wrap around the player to store away. Their cord also remains much less tangled than the 888's cord. I did the Croakies mod to my KSC-35s so they're no longer so easy to put on and off, plus they look a tad out of place in public I still say. It's also a pet peeve of mine to leak music around me, which the KSC-35s do. I personally prefer to use open air earphones regardless of outside noise because of hygeine reasons...after on/offing the EX70s 2-3 times in a day, they tend to pick up dust really easily because of oil and sweat from the ears, and if you stick that into your ear too much, it'll be a good way to get an ear infection. So those are out for me.