
Easier to build than pneumatics? Maybe?
Part of the appeal of pneumatics is that there's no tension on the brake pad when you are trying to trigger it (like if you were trying to pull a peg out of the springs or something, it is under tension and could jam). With the pneumatics, you flip a switch and it goes.
The obvious downside to the pneumatics is that unless you have the lego version already on-hand, it is a lot harder to acquire something that would work well than it would be to get a set of springs.
I don't know which would work better. I imagine they could both work quite well, if triggered accurately (my problem).