We have several CJ's and YJ's on both sides of the Fiberglass/steel/alum replacement body fence. All sides throw rocks and complain about their choice. Fiberglass, needs a full wire ground run through it and extra body supports needed because the bouncing and trails crack the body, Alum needs ground wires also, alum body and steel wire rings corrode at different rates and fail often, just run a ground wire package, trust me. Body repairs and painting need special handling on alum. Steel, is well steel. Depending on MFG.
No one stands out, but we have more alum body replacements out here than anything else, because alum is a little lighter, but drag it across a rock and you will curse your self for not buying steel. (aluminum will gouge and ball up on the rocks making an interesting gouge mark to repair.)