I don't use the power jumper for attaching bands in the power rack.
I use regular jumpstretch bands. The main reasons I use the lightened setup in the weight room more than the regular bands at the bottom setup are that I beleive for jumping and running that the eccentric strength developed via plyos and sprints carries over much better running and jumping (funnily enough this should come as no big surprise), and that the extra eccentric load of bands in the power rack tends to cause more soreness (longer recovery).
As a result I use the band resistance sparingly or with lighter loads for more explosive movements when I am trying to reduce the impact on an athletes joints (if they are playing a lot of sport for example, but are already pretty strong I might incorporate fast and explosive speed squats with the bands as a means of developing explosive strength without using more jumping drills).
One final reason I use the lightened setup more is that I don't feel the need to be as precise with the weights. Here is an example in my own training. I do a lot of heavy front squat singles. I worked up to 6 singles at 165kg but was really struggling to increase the load past that. SO I started doing 4 singles with 165 and then another 4 using lightened band setup but with an extra 20-30kg on the bar. A month later I was able to 5-6 singles with 175kg.
I didn't put too much scientific thought into this, I just slapped some extra plates on and then added the bands to help me out at the bottom. Getting used to the extra weight in your hands and the gradual reduction of band assistance really forces you to accelerate up through the lift which seems to have helped up my strength nicely.
