Sir Inigo, for cans-only mixing, SR80i or the M50, sino mas honest?
Personally kasi I love the SR80i, super honest (for the price) but since it's open back, the bass is felt more than it is heard, and the response is like listening to a vinyl record, which I find nice. For listening purposes, Grado talaga. I just don't know if they're good enough to mix with too. I'm just afraid I might get a lot of low end mud when mixing with the Grados.
Wala akong experience with the SR80i (matesting nga yan someday). Yung M50 naman narinig ko na, I think useful yung high-mid response nya, kasi naririnig mo yung mud, kaso medyo too ear-friendly sya (smooth?) for my taste. My ears are adjusted to Sennheiser HD280, which sound relatively harsh. People say that the more neutral the headphones are, it's better for mixing, kasi the point is to achieve a mix that translates well into other sound systems.
I think in the end naman, what's important is how your ears have adjusted to the headphones in so much as you can already hear the sounds in an objective way, more than how the headphones actually sound. If you feel na the Grados accentuate some frequencies, than you might want to anticipate that and reduce it, then test the end result with cheap earphones. I test with stock speakers in my car and stock headphones on my phone, then compare with other songs in my playlist.
I shift back and forth from Senn HD280 and my monitor speakers (Yorkville YSM1 and Yamaha MSP5) and they all sound different. I use all of them to check levels, balance, etc, pero I particularly use the HD280 to check for detail (because I don't hear the room), the MSP5 to check for mud in the mids, and the YSM1 for bass and overall balance. I had a Yamaha NS10 once, and in my room I thought that they sound just like my HD280 on my ears. So you know, madaming factors chuvalu.