I've use them all (MyProtein, Kaizen and MusclePharm) and I'd recommend MyProtein over the others. Cheaper, great quality, backed by Labdoor testing (https://labdoor.com/rankings/protein/quality) and lots of flavors, most of which taste great! This way you don't get fed up of the same old taste over and over.
Didn't like the bland taste of Kaizen and the MusclePharm's taste was disturbingly inconsistent. Not sure what that was all about so I just stopped buying it altogether.