I have no brand loyalty. I have Shimano, SRAM and Campagnolo on different bikes. They are all good. SRAM is the lightest( I think), Campagnolo seem to elicit oohs and aahs from "Italian" purists on my Italian brand bikes. Shimano is very common. They have differing ways of shifting and aesthetics, but I have had no issues with function. You should be hard pressed to find cons on any unless you really go looking for them. Some will argue just for the sake of arguing.