Here's my opinion.
We are on our 3rd set of tires. Followed the original 25580R 22.5 Michilins with 25570R 22.5 Dunlops. Last year, we installed 25570R 22.5 Coopers. Coopers are American made, available everywhere and tire of choice at my last (before retirement) distribution center.
70's have a higher load capacity than 80's and are not as hard to find as 80's. HOWEVER, they are about 2 1/2% smaller in diameter than 80's. Your speedometer will indicate slightly faster than actual, and your odometer will also read slightly over actual. (I believe there is a fix for that, just hasn't seemed important)
Here's another thread on this subject https://www.winnieowners.com/forums/...-a-355405.html
Fair Winds and Following Seas