I think that best "bang for the buck" is a question that only you can answer.

Shimano makes so many different component groups that I can't keep track of them all anymore. They all do the same things and they all, even the cheapest Tourney ones, do the job. The more expensive ones are just a little crisper operating and look a little bit nicer. As you go up the price brackets the functional improvement tends to progress at a gradual steady rate. Prices, however, jump up geometrically. Most riders are looking for the optimum place where the price line and performance line cross and everybody draws that graph differently.

If you have an unlimited budget and are only satisfied by the absolute best, all you have to do is ask. If you only have $60.00 to spend, the cheapest Walmart offering might benefit your lifestyle immensely. Either might well be the best bang for the buck for a particular buyer.