I agree quite a bit with Elgofre about the HD25s. Yes they're aggressive but it's something most will enjoy. The M50s are good also but I wouldn't say they are any less guilty of sonic truth for studio work (if by that you mean creating music). I find the M50s a little muffled and overzealous in the bass and a bit lacking in the upper midrange. Although they are bigger they wont be a super comfy circumaural experience like the big Sennhiesers or Beyerdynamics. The HD25s might be on-ear, but at least it's more obvious what you're getting and they are much nicer for travel or leaving around your neck too. Hmm what else... both have removabke cables, if we're talking about the M50x, but that one is modular, I think.
For studio work I would say the M50X's, full sized headphones have better imaging properties and the more restrained treble falls closer to neutral than the HD25's sound signature.
OK... these or Audio-Technica ATH-M50X (£125) for studio work ?? too many options oO #headhurting
Superb headphones, the HD25s are among my all time favourite headphones of the dozens of premium pairs that I've owned or used over the last few years. They won't suit everyone with their strong clamping force and some listeners can find their bright sound signature a bit fatiguing, but that aggressive sound is why I love them as a listening pair, and their reputation as a professional's headphone is legendary! For anyone looking to spend under £150 on an on-ear headphone for enjoying music or any kind of audio work, these are one of my top recommendations. Not to mention they're built like tanks and can last a lifetime. It's also worth noting that this is the version with a 3m coiled cable, which is great for home/DJ use but less so for portable listening. If you want them for using on the go, then the HD25-1 II Basic Edition (same headphones but without some accessories like a carry bag or velour ear-pads) cost £111 on Amazon while the standard edition of the Sennheiser HD25-1 II costs a little under £140, with both coming with shorter straight cables.