[cadillac_al]

I think either wheel will work for you and the 10" wheel should tuck the wheels in an extra inch.

What I do know is an 8" wheel was too narrow for my 12.50 tires on the road. I couldn't get the sides of the tread to touch the road unless I had about 20 lbs of air pressure. I had to switch out to 10" wheels to get the tread to lay flat on the road. I guess off road drivers don't mind an 8" wheel with 12.50 tires because they get more rim protection with the narrower rim.

I don't "think" a 10" wheel would be too narrow for a 15.50 tire but it's hard to say without trying them. When I used to run 14.50 wide tires I think they were on 10" rims but I can't really remember, could have been 12" wheels I suppose. I think your concern about tire shape is valid.