Okay so take it easy on me, I'm a novice but why is SI not beneficial at the trolling motor?

And just to be clear a SI is a SI and DI both? As in, I can swap back and forth? If so, that's what I'm going to get.

EDIT: I watched a video, I understand it now. I will be going with SI

If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land. 2 Chronicles 7:14