Depends on what you like in your music. I know a lot of people on this forum will flat out turn a blind nose up at the beats studio, but their sound signature is geared for the type of people who want the oomph in the bass. I listened to the beats studio briefly in the apple store from time to time, and I will say that their bass is overly powerful, the mids are not very clear, and the highs are no where near as sparkly and clean like the M50s. However, the big thing they do have is a punch to their bass, mostly from a large mid-bass hump, it's the type of bass that will move air.
The bass of the M50s I can describe as more appropriate and well mannered. It's considerably more detailed, extends lower and gives a slight punch for drums in well recorded songs, but not quite the punch the beats have. If you try to eq for more bass in the M50 as well, the bass really starts to drown things out. The bass on the beats is more hollow sounding, probably because it doesn't extend as low, but it somehow manages to give the punch (even though it's far from a crisp and tight bass) and not completely drown out like an eq'd M50's bass.
Overall the M50s do everything better (including build quality and comfort), but they won't have as much punch to the bass.
I'm not sure what the M50's bass punch would do with an amp (I heard a small amp/dac does wonders for their bass punch and tightness) but I do know it's a more clean and refined bass, but not the true punchy type of bass.
I think what you should most likely do is get the M50s, and then get a cheap dac/amp for them later on if you feel they need a good punch to the bass. Also note people will have differing views on the M50's bass. Some will say it has too much bass, some will say it doesn't have enough. You'll most likely get more straightforward reviews on the beats though