15x8 with 4.5 backspace or 15x10x 4.0 backspace??

ok guys i am gettin 33x12.5.15 tires and currentely am runnin 32x11.5 tires on 15x8x4.5 inch backspaced rims. I have a little rubbing when i turn the wheel all the way in the XJ, do I want to move up to 15x10 with 4.0 backspace for the 33's which are 12.5 an inch wider which translates into roughly half an inch wider on each side of the rims? Someone mentioned on a post that 15x10 rims dont hold a bead when you air down offroad as well as 15x8's do, anybody else have any input?? Also have heard that you get better tread wear pattern with 12.5 inch wide tires on 15x10's than on 15x8's???

TIA
Joe

15x8 with 3.75 backspacing, is where it is at!!!