I would say that they are 2 completely different feelings. Yes, you do get the stim effect from the RPM (the insane drive to workout) but you also get the feeling of increased testoterone which makes you want to lift harder, and also may give you a little aggression! You get the energy, but definetly don't get the crash like you do from Ephedra. I love ephedra, but I hate the crash. RPM is much better, in my opinion, and is much safer for you. Just my 2 cents.