I suppose the micro-controller is nice, but if you only need one speed why bother.
Now I just need to get a DSLR instead of my Canon AE-1 Program.
Also, if you're looking just for better image quality, a DSLR isn't anything special. It's just a camera with a mirror. You can get any APS-C or larger-frame sensor nowadays that aren't DSLRs.
Depends on whether we're talking about open-loop control or closed-loop control. A stepper motor can only move in half-jumps or full-jumps. The size of the jump is intrinsic to the motor, and can be reduced with a gearbox. If we're doing closed-loop control of a DC motor, the resolution is limited by the feedback encoder, which typically has a resolution a magnitude or two higher than a stepper motor's.