I'd love a 24v trolling motor. So much more longevity. Not only throughout the day but with the life of the batteries. I would be considered a heavy, "power user" of my trolling motor, maybe 20 hours a week. I find that even when I buy a top quality battery and am diligent with my charging, the batteries last 2 seasons before they start noticeably loosing capacity. A 24 v system, buy very good quality batteries and they will last much more than 2 seasons.
Anyway, I have a 12v 50lb Minn Kota PD and it pushes my 14' deep V about 5mph on full.