I've heard great things about trolling motors with iPilot or spot lock, that locks you on a spot without you having to touch the pedal... If I were buying a new one, I would spend the extra money to get that for fishing out deep.
I think either MotorGuide or Minn Kota would be great units, but keep in mind Minn Kota syncs up with Humminbird and Motor Guide syncs with Lowrance. That might play into your decision.
If you keep your eye out on the classifieds, there are trolling motors for sale quite frequently.