Wind and sun can dry things out down there, better to be safe than sorry. Besides, imagine a Honda towing a Honda with a spinning prop. Is it pushing or pulling?
I have heard from the elders taht a spinning prop is better to apoint because a kicked up rock on the drive bounces off the prop without much damage, but a prop in gear not spining can take some serious dings. I have always had mine spinning. but that is what I have heard for a no gear reason.
Have never had my motor in gear on purpose….never really thought about it. I would think a spinning prop would be better for the above mentioned reasons. But then again, I usually tow my boat about 60-70 miles round trip when I’m fishing around here.