Nikon vs Canon is more of a religious debate than it is anything related to which is actually better. I've owned both brands (use mostly Canon now, but all my film stuff was Nikon) and you can't go wrong either way.
As far as portrait lenses, the 50mm I use goes to 1.4 but I shoot mostly at 2.0-2.8. Obviously it will depend on where the lens is sharp, I think the 50mm I shoot is sharpest at 2.0. My goal with portraits is usually to have the eyes tack-sharp and the skin just blurred enough to make it soft so I adjust my depth-of-field accordingly.