I have the exact opposite view th that expressed by WhirlyGig.
I am glad I trained on the R-22 and then transitioned to the H300.
Still it does not matter one way or the other.
Most people find the R-22 much more difficult to fly than the H300, as it is very light and exceptionally sensitive on the comtrols compared to the H300.
My instructor advised training on the R-22 and then moving to the H300, as most students found moving from R22 to 300 easy, but many foundvit a challenge to go the other way (a challenge, but very doable with a bit of extra time).
It is alsosaid if you can fly an R22, you can fly anything, but I haven't heard it said about thr H300 before.
In the end, when I went to transition onto the H300, I was amazed at how stable and almost boring it was (just as a good training helicopter should be).
So you will be able to fly both easily, and thevone you train on will be the one you prefer over the other (I love the twitch lightness ofvthe R22 and the fact it makes you do auto's perfectly, as you can't get away with near enough. i think this makes you a better pilot (to learn on the more difficult machine), but probably justbthat having trained on the 22, I am prejudiced in favour of it.
In the end, both will teach you to fly well if you have a good instructor, the 22 is harder to fly, the 300 safer, and you will transition more easily frona22 to a 300, than from a 300 to a 22.
Enjoy the journey.
John