There is no such thing as a one size fits all situations, as in type of fish your targeting, or in the type and size/weight boat you are using it on. Problem with even the smaller gas outboards, is trolling speed control when very slow speed is required without dragging something behind to slow you down.
The largest size electric with multible batteries certainly isnt a requirement on every boat, nor is it advisable to do that.
I have 2 boats, one is a 17’ fiberglass center console Key West, and the other a 14’ aluminum jon boat made by Alweld Boat Co.
I have 55# thrust Minn Kotas on both of them with one 12 volt deep cycle battery on each. I primarily troll with live minnows or small jigs for Crappies, requiring a very slow speed of plus or minus 1 mph. You will not do that with a gas powered engine.
Think about this, how fast do you turn the reel handle when retrieving jigs when Walleye fishing, And why would trolling be any different?
I would be better served with an 80# set up with 2 batteries on the 17’ glass boat from the duration standpoint, but not the speed. The 55# will push that boat far faster than is required, just not for as long a time frame as the one on the lighter boat, and i could add a second battery. That said i have no problem getting 4 hours of steady trolling with it with a fully charged battery.
