Overall SQ: the Mad Dogs seem "warmer" to my ears and the highs seem more polite than the Shure SRH1540s. This might be due to the "flatter" response on the former. Mad Dogs bass seem to "hover" around a bit more giving the illusion of a "fuller" sound on the lower frecuencies (i.e. it's slower) while the 1540s mid-bass seem to be a bit increased and can sound a bit boomy and spread to the lower mids if the track is very bassy.
Mids are tastefully done on both headphones but I feel that the Mad Dogs fare better since the mids are more forward. Vocals for instance sound very good on the Mad Dogs. But were things get interesting is in the imaging/sound stage department. Since the Mad Dogs provide a bit of a more "closed-in"/narrower sound the more open sounding 1540 takes the cake and even though mids don't "feel" as forward due to more air and separation,
it is great especially with genres such as Salsa and Merengue.
Highs on both are extended but not at all emphasized like let's say the Alpha Dogs or other bright cans such as Shure 940s, Beyer T5ps, Yamaha MT220s, etc. etc. Though the Shure's are definitely more airy. Tonally both are similar as well. Listening to specific Piano pieces I sometimes sway more to the Mad Dogs way due to the more "intimate" setting but then I put something funky as Jon Cleary's "So Damn Good" which although piano is mostly A center piece, the Shure eats the Mad Dogs due to the very good instrument separation and a bit faster bass response. (fun track though and COMPLETELY RECOMMEND IT!
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So basically at this point is up to preferences... I do like 1540s imaging as it reminds me of their 1840s which I found it excelled on this, but the Mad Dogs are a bit more "natural" sounding, more even and with more in-your-face mids.
Isolation: Mad Dogs win. They block outside noise better due to the AWESOME-ASS-KICKING Alpha Pads and noise leakage is very minimal. Not so with the Shure's. Seems the alcantara pads although making the headphone very comfortable it also makes sound leak more easily. So if you like to crank it up, the Mad Dogs fare a whole lot better.
Comfort: a Toss up. I LOVE the Alpha Pads (haven't tried those on the 1540s but I think member Change is Good has) and I feel the fit of the Mad Dogs is excellent. The Alcantara pads on the Shures are awesome as well and them not being leather, they don't induce much heat. But fit might be a problem. As some people have mentioned, the Shure's extend more outward than downward so not only do they look weird, depending on the shape of your head they might feel weird or even uncomfortable.
For the money, the Mad Dogs are an EXCELLENT buy. Though you still need to spend more $$ in amplification (this is going to be MY next step personally... I think I have the headphones I want at the moment) for them to really REALLY shine. Shure SRH headphone is excellent even from my FiiO X3, Cowon C2 and AK100 MK2!
For your preferences (Rock, Hip Hop) and budget I believe both headphones do well. I would probably go with the 1540s just because guitar crunch and instrument separation and a bit more airy characteristic but for Hip Hop I slightly favor the Mad Dogs! Again... this is a toss up... so I know I'm not making things easy for you! LOL
Maybe more members might be able to chime in, but this is how I feel. I feel both do a very good job overall so I guess it will come down to things like isolation, leakage, imaging preference, box contents, ease of driving them, etc. Also, you can look into other (and maybe even cheaper) alternatives such as: Shure SRH840s (I feel that the 1540s are an enhancement/refinement of these headphones), SoundMagic HP100, Audio Technica A900X (with better earpads if possible) and even the Monster N-Pulse (not the N-Tune) headphones. I have to say though that for "Rock"/Metal, etc. I actually prefer a bit more brightness with me headphones and both the 1540s and MDs have a warm tilt and more evenness throughout...
Thanks and Good Luck!!