It will be close, almost indistinguishable. Over time though, the two-stroke Opti may need to have the plugs changed more frequently than the four-stroke if you troll a lot.( I mean a lot.) That's because, efficient as the Merc DI system is, the two-stroke is still burning oil with the fuel. But really, you'd have to be a charter capt or towboat operator to really see the diff in plug change intervals. I mean, I had a pair of 150 Opti's on a center console project boat a few years back and we trolled offshore for probably 80 hours during he course of a season and never had a blip.
Both engines are Smartcraft enabled and with the right control box, gives you the option of using "troll control" which electronically stabilizes the engine at lower speeds.
The Opti has a 60-A alternator to the Four-Strokes 50-A charging capacity. Displacement is greater for the four-stroke, so you could make the case that that engine is "torquier.but we are comparing an inline 3 to an inline 4 with different bores and different strokes....
Hope this helps