I have both a cpr bakpak and a prism. I prefer the prism. The bakpak requires far more tinkering than the prism. I think the prism is more efficient as well. Finally, the bakpak is quite noisy. Oh yeah, the backpack is much more visible in the tank. The only thing sticking in the tank for the prism is the intake which is a clear smoke color. The surface skimmer attachment on the prism it also unobtrusive. The surface skimmer on the CPR is bulkier. If you want the skimmer and bubble stopper attachment for the CPR, then your really talking ultra bulky. (there is an internal bubble killer for the CPR)