I use a Hasselblad, so using a macro lens is pretty much out of the question-- it costs at least $800. So I only have one lens, the normal 80mm; I also bought an extension tube because it's a lot more portable than the bellows, (and it's cheaper!). I doubt I'd ever buy the macro lens; unless I started earning a ton of money, I'm perfectly happy and content with my normal lens with an extension tube; though I do plan to buy another extension tube or two in the near future.
I've always been very happy with my macro shots, though my "macro" shots are really more like close-ups, when a large flower might fill the whole frame, not the aphid on that flower!
Anyway, I think the macro lens would ideally be a bit sharper, but I doubt you'd notice any difference between it and a normal lens with an extension tube/ring.