I personally just went through the exact same situation. I have an '07 MH that had '05 tires. In October I made a change that I am pleased with. Below is the entry I posted to the forum two months ago.
Changed My Tire Size
I am writing to let you know what I recently did with my tires. Hopefully, it may help someone else.
My 2007 Mountain Aire 3991 is on a W25.5 chassis and had 2005 Michelin XRV 235/80/22.5 factory tires with 35K miles on them.
On 10-21-13 I put on 6 new Firestone FS560plus 255/70/22.5. These tires are H -one load range greater , a fraction of an inch less in diameter, and a fraction of an inch wider than the 235's. In addition they are a popular size for trucking. This makes them more available and priced more competively than the factory 235 size. They have a greater weight capacity so I can run with approx. 10 psi less in each wheel position than before.
I was torn between spin balance w/weights and adding balancing powder. The shop had both but recommended spin balance. Their reason was on rare occasion they find a new tire that requires too much weight to balance (manufacturing error) when they spin it. Using powder would not require spinning and therefor they would not pick that up. The 4 rear tires required a few ounces, the 2 front tires took zero weight to balance. I still am on the fence between the two balancing methods.
I was also seriously considering BF Goodrich and Toyo at other locations in the same town. All three brands were within 150 bucks of each other total for a set of six tires.
I purchased the tires at GCR Tire Center just north of Eugene Oregon (land of no sales tax). The date code on the Firestones are "4013". My total cost for 6 tires, mounted, balanced, new stems, take old tires.... out the door = $2160.
George R. - Fulltiming since January '03
2007 Newmar Mountain Aire 3991
2012 Chevy Malibu LT1