According to the Anandtech Surface RT review, where he managed to get a hold of an Atom tablet as well, the Atom tablets will have anywhere between a 20 to 50 percent performance advantage over the Tegra 3 tablets... How they compare to S4-based tablets is still uncertain. Unless Atom tablets have something like 6 hour battery life and gets ridiculously hot (something I doubt) they will be a way better buy than most RT-tablets...