Heya,
Both are excellent but in their own ways. I found them both comfortable. Some people find the headband of the AKG's to be a problem, but I'm not sure if they're bald or not. I have hair on my head, and never noticed anything uncomfortable about them. Both have comfortable cloth cups. Good deep cups at that.
Sound wise, I think the MA900 has more low end response. So if you're seeking a really wide sound stage, along with good extension into bass, the MA900 would be my pick for that. The Q701 has a little less low end response and a similar sound stage, good and wide. I would basically go with either one if you want a neutral, but warm sound, with a nice wide sound stage, but get the MA900 if you want a little more low end ability, or go Q701 if you are ok with a more shy approach to the low frequencies. Depends on your preference. I prefer more body in the sub-bass for example, so for me, I go with the headphone that has that ability more. Sound stage on both are equivalent to me.
Very best,