Looking for some help and advice on new tires - specifically in regard to tire size.

I currently have the stock Hankook 235/70R17s that came with the truck when I bought it. They are ready to be replaced.

I routinely tow a 6400lb trailer (short distances only) and will be towing a 5000lb Travel Trailer (longer distances).

I was looking at the Michelin LTX M/S2 tire, and was considering getting the larger size 255/65, but don't want to spend the extra money if I don't have to.

Can anyone tell me whether upgrading to the 255 is worth the added expense - or is the 235 adequate (and safe) for my purposes?

Thanks!