That's a decision nearly every fisherman has had to make at one time or another if they have been doing it a while and have owned some boats. I have a 16 ft Lowe Big John with some wood decks in it and some other stuff adding weight,along with the fat boys who ride with me sometimes. I bought it used with a 40 lb Minn Kota on it. I figure to upgrade when it gives up the ghost.The more powerful motors give you a much wider power band to control speed in the wind. When it gets very strong I just have to kicker to 5 which is too fast or strong where as 4 just wasn't quite enough.
I have a 24 volt 80 lb on my bassboat.To be able to choose between 12 or 24 volt and 5 speeds in each range just lets you find just the right amount of power. But in the right conditions even it is maxed out and thats on only a 17' fiberglass.
I have caught thousands of fish in that jon boat,its seen big and small water ,you learn to work with what you have. But now if you'd offer to swap me straight up for a bigger motor right now I'd say heck yeah you kiddin'