One larger motor is superior in just about every way. More compact, more efficient, cheaper, etc. However, this particular application demands a certain form factor that is more of a flat plane than a large cylinder. It's certainly less efficient, but should yield interesting results nonetheless.
Given that these motors are cheap, I don't doubt the work done by each will be perfectly equal. But surely they ought to be close enough to where supplying equal current to each motor should generate close to the same torque? If you suspect that's not the case, then perhaps I'll need a way to control the torque as well.