There are two major "types" of PSU. (Or more like 3, third being Crap, blows up when it is loaded with half of rated capacity, bad regulation, too much ripple)
Non-crap cheaper ones are group regulated (Only load level on 12v line is used for regulation), more expensive ones are independently regulated (each rail has its own regulator).
EDIT: Also different PSUs have different min load requirements.
All this makes choosing the best "Amiga compatible" PSU very very difficult.
Last edited by Toni Wilen; 31 August 2012 at 18:01.