IMO, they're all the same when it comes to leveling kits. I mean, how much R&D do you need on a metal puck, really? I have the Pro-Comp 1.5" spacer (actually .80") that mounts on the top of the strut. I bought it from Four Wheel Parts for $150 because it was the only place that had anything in stock and I needed it that day. I just ordered a 1" bottom strut mount spacer off of eBay for $25 and I'm pretty sure it's the same material. If I had to do it over, I wouldn't hesitate to buy a no name spacer kit for half the cost. A lot of what you're paying for is the name on the box.
Now, as someone else earlier in this thread pointed out, things change when you go above just spacer leveling kits and start getting into actual lift kits. These actually do have some R&D built into them to measure angles and where to notch frame and whatnot. If I was going to go that route, then I'd put a little more stock into a trusted name.