I buy the lower cost imported batteries, but to get MB quality electricity I take all the electrons out and replace each nuclei with nuclei extracted from discarded MB batteries from the local MB wrecking yard. Sure it takes some time, and special precision tools, but its worth it in the long run.
Seriously, though, let me cast two votes, one pro, one con.
I'll cast a vote AGAINST current Sears DieHard batteries. Used to be good quality product, backed by a good warranty. Now junk, backed by the same good warranty. Sure you get new free batteries, but who wants to keep getting jumped or towed to pick it up. This has been my experience in all my cars, not just the MB's. Sears must've changed manufacturers at some point in the last five years or so.
I'll cast a vote FOR Interstate batteries. I've had good luck, my friends have had good luck. Seem like solid product.