I can't say anything from a user experience, (1st time pontoon owner), but I have been researching the same topic. What I have learned from motor dealers and 2 owners.
1. Bow mount is best for boat control.
2. 70+ lbs of thrust minimum
3. 48" to 52" shaft
4. All the motors I have reviewed at 70+ lbs thrust require 24 volts. = two 12v batteries, or, 1 big old tractor type 24v.
5. My boat is not set up for a bow or stern mount motor which makes me think about how to deal with motor to battery cables.
6. So far Minn-kota brand seems to be the direction I'm heading.