Bottom line....better ring seal, longer life, more HP/torque. Some people go so far as to install a torque plate on each head, use the same style head gaskets as will be used on the final assembly, run warm water through the block, torque the main caps to spec.......every little bit helps. Diminishing returns, but returns none-the-less. (Certainly can't hurt!) It's just a matter of how much time & money you want to invest.