Did my PPL in an R22 and CPL in a H300CB. Also just gone from Texas to Florida in an R22 (still recovering :-).
IMHO, the 300CB is a better training machine because the RRPM is more stable and there is no governor - just correlator and throttle which gives a student better appreciation of power / overpitching. For example, you notice as you gain translational lift that you need to roll off throttle now that induced drag has decreased - just an example of something I never appreciated in in the governed R22 during training. It's also better for training for full down engine-off landings due to greater inertia in the head and it feels tougher. Every school I've been at is hesitant or simply does not permit full-downs in R22s. Also, instructors at my school like to do throttle chops when you least expect it which I have found extremely valuable. Some of them have said, they don't do chops when teaching in R22s as the required reaction time is too fast.
However, the 300CB doesn't want to fly - the R22 does and is a faster, more 'fun' machine. It's extra speed and space under the seats make it better for x-country.
I'd recommend doing PPL on a 300CB then going R22 later but I don't think it's really a big deal.