I would demo the 300 and R3 if you can.
I demo'd the R3 at Snow City last month and preferred it over my 300. Don't get hung up on ABS; I've put ~36,000 KM on my 300 and I've never once needed it.
I couldn't really get a good feel for the suspension on the R3 during the short demo, but the 300's suspension is crap. If you're tracking it you will want to spend money on suspension immediately. The front DIVES under any hard braking, and the rear has awful rebound (often feels like it's just floating).
But the 300 has the advantage that the market is already flooded with parts since it shares so much with the Ninja 250. There's also a lot of great, easy, cheap mods you can make (e.g. you can swap a GSXR-600 rear shock onto the 300 almost effortlessly for less than $100).