Like most others, I trained on an R22 and finally wound up a few years later owning one. I did look hard at the Enstrom before I bought and was quite taken with it, but as HR says, Enstroms are found in localised clusters in the UK and I am not near enough to a cluster. I have never flown a 300 so cannot comment. As was suggested above, your best course would be to have a T/L in each and see which you like. I have only flown 4 other helicopter types in addition to the R22 and they all seemed very stable in comparison.
I would echo the comments re the Rotorheads forum - they are extremely helpful to beginners and there is a huge depth of knowledge there. Don't be put off by the "professionals" tag.