[outfield]

I ran 15x8.5 slot mags for years on a 74 K10, the off-set was such that the tires were right out at the edge of the fender wells.
So my point is, the off-set has a lot to do with the decision. If the 15x8's set the tires out to the edge of your fender wells, I would run them. If the 15x10's stick the tires out 1 or 2inches from the fender, do you want to deal with the rock chips and water and mud spraying all over the truck every time you drive it?