Do you suggest the single rail because it can handle more amps?
I suggest a single rail because it's less likely you'll have overload rail problems or blown rails. The single rail designs are rock solid except maybe a user can ask too much of the cables and melt them (don't ignore hot cables, spread the load to more cables or use thicker cables) Good PSUs have 18AWG wires, cheap ones may only use 16AWG, and are much easier to melt!
You usually get what you pay for with single rail, a Corsair 750W PSU will have a 62A/744W 12V rail, but that Warlock 900W PSU only has a 696W max on the 12V rail, and someone comes along thinking they can stick 900W on it and it blows up!