Does that mean the SmartPower PSUs don't get put inside the case, but outside of it? And also does that mean that you can dissconect wires that you don't need?
It means it has cables you can plug into the PSU instead of having them all already built in. This lets you use only the cables you need and not have unnecessary clutter from ones you don't.
I don't know of either too well but I have an Antec NeoPower 480 in my system and I can confidently say that Antec make quality power supplies and Modular configuration makes a difference. The Neopower is modular if your wondering.