I taught students on both types and I always found people progressed faster on the 300CB.
Even if the R22 is a little cheaper you'll find you will hover and solo sooner on the 300CB. If you plan to train in the US then you'll also not have to fly 20 hours before going solo in the R22 due to SFAR 73.
As you said you're aiming for a CPL then Arm The Floats has some good advice, get the PPL on the 300CB and then transfer onto the R22 with a bit of experience.
Which school were you looking at?