As long as they are rigged similarly, (power tilt, tiller or remote) the carburated four-stokes are pretty much the same these days.
The only trolling motor that offers fuel injection for incredible speed control and a true 15 amp alternator is the Evinrude 15HO.
It's only 60 pounds heavier and keep in mind that the engines thrust is the most significant force on your swim step. Not the weight.
I do understand the hassle of strengthening up a bracket but in all honesty, if my trolling motor mount was 60 pounds away from failing, I would be doing some serious beefing up!