The best and cheapest power bleeder is a competent assistant operating the brake pedal while you operate the bleeder screws.

Since I rarely have anyone around to help when I need them, I use the motiveproducts bleeder and I'm quite happy with it. I have only flushed brakes with it, however. When I open an ABS system I will bleed the system using an assistant and on some cars will have to do this with the engine running for the power booster to help increase pressure.

Good luck,