Nars blushes are one of the few times I cheat on MAC. I find the Nars quality to be so much better. I feel like the powder is more finely milled and applies more smoothly and evenly. It's true that Nars doesn't have as extensive of a color selection as MAC -- but I think they have ample choices for every shade range you're looking for. My personal go-tos are Luster (warm golden color with a bit of peach, great when you want a neutral flush without drawing attention to your cheeks or making them pink), Angelica (cool pink, very bright in the pan, but creates that perfect pretty pink flush when applied) and the all time cult favorite, Orgasam (peach w/ subtle gold shimmer -- pretty much looks good with everything and super low maintenance to apply). I have a ton of MAC blushes in all kinds of shades, but I find that I keep reaching for these three Nars colors again and again and that they are all I really need to keep me happy.
Hope that helps!