If you are in heavy current/wind alot you might want to consider 24V. I talked to the people at MinnKota before I bought mine and they say that if you "overpower" with iPilot it causes the unit to jog more. Overpowering is very hard to determine on boats between 15 and 17 ft and thrust need is determined more by conditions than weight.
Does the 50 you have pull the boat well in the conditions you normally fish? Are you planning on fishing new places that you know have stronger current or have stronger winds alot?
I decided to go with 55lb model on my 15ft SeaSquirt, with published weight of 550lbs, 197lb motor, 72 lbs of fuel, 100 lbs of batteries (40lb starting, 60lb trolling), and 300 lbs for me and my gear. Slack wind and no current I get 4.8MHP at full power, 2.8 MPH dead in to 10-15 wind with no current.
Pool ... I absolutely love my MinnKota iPilot mine is on a Riptide 24v system. Our boats should be similar and I have no complaints. The anchor feature is my favorite, well and also the GPS track feature. I don't regret upgrading mine.