Of course you have to ask yourself, why does it really need leveling? A nice spring / shock setup shouldn't be sagging, that's usually a determining factor of very old an worn out suspension components, or just a crappy spring / shock combo.
The right way to do it would be to get a nice pair of shocks and springs. However, if you want to go with a leveling kit, they're all pretty much the same. Just polyurethane spacers you're shoving in there. I don't think I'd worry about the brand or performance comparison, they're literally all the same thing... just a chunk of polyurethane.
I guess I was thinking more from an esthetics aspect. Seems like a quick and cheap way to get a slight lift without going whole hog with a suspension lift.