I would go with the wheelchair motors, simply because I doubt that the wiper or drill motors would be powerful enough. Battlebots do sometimes use wiper motors, but I would guess thats for weapon actuation, they are often prewired for reciprocal motion which would be helpfull for a hammering battle bot, but a problem for your platform.
Also, whatever you use should be a continuous service rated motor, which drills and windshield wipers are not.
