That all depends on what the width of the tires are, what you intend to do with them and what kind of tires.
If you going with 12.50" or less go with 15x8". You have more protection from beads popping when aired down. If you are going with anything wider than 12.5" I would go with 15x10".
If you plan on getting wider tires down the road, go with the 10" wide rims.
<A HREF="http://albums.photopoint.com/j/AlbumIndex?u=1764091&a=13613281&f=0" TARGET=_blank>
Just an average YJ with 36s</A>