Be careful when you take 1MR for the first time...definitely start out with half a scoop. I felt like my face and ears were going to peel off the first time I took a full scoop! That being said, the 1MR is great for energy, but the taste is God awful.

I have not personally taken either but my under standing is that Pump HD is an Improved version of 1 MR

Haven't tried Pump HD (Think it is on my short list thought)...but have to agree with the 1MR crowd. Works good, tastes very very bad.