i have 10x8 for my rears, i have been riding on an mx track, so the smaller rim= more side wall which is nice for side corner bite, (and incase your wondering, the 18's in back are awsome, i love them) and my rims have the reinforcement ring in them, which they have held up nice for my buddies and i, even with the abuse of the track.
I have t 9 rims both regular and rolled edges, they dont like rocks...thats all I have to say. I bent them hitting stuff, rode them home flat, hammered them back and they sill hold air. I guess thats ok, but Id rather not have to run flat. My next set of rims will be ITP baja but I will weld the rings in myself. So far my sock rims have held up the best.
rings on the bajas are rolled in, I am afraid of them getting loose so when I get mine, Im gona hit em with a welder. I think people are afraid of the welder geting the rims hot and warping, but Im not really worried.