Owned a RR300 for a year, had plenty of rides on the Xtrainer and finally got to ride a RR250 for a few days. Heaps of guys asked me for a comparison of all three. What did surprise me was the Beta RR250 still had a lot of lowdown grunt and a very linear power delivery. Even with the softest power valves setting I remember my KTM 250EXC had distinctly less lowdown power than a 300, but still had a power surge as the power valve opened. However, the RR250 was very smooth throughout the rev range, and with the power valve turned in most of the way the power at low revs was good too. The 2016 RR250 has also had changes to the porting for more grunt. While the RR300 has a butter smooth engine, that extra lowdown power can get less experienced riders into trouble so the RR250 could suit less experienced dirt riders better.
BETA XTRAINER
The Beta Xtrainer? If you like your slow technical riding in hard terrain, this is your bike. It is also great for the less experienced or shorter dirt rider, with a seat height an inch lower than its big brothers, and similar power characteristics except they have knocked some of the top end power off. If you do like the occasional fast blast, then the Xtrainer won't be as capable with that deliberately soft suspension setup, light front end and mild top end power. But a major plus is it can be up to $2000 cheaper than a RR300 which allows a good budget for beefing up the suspension, a steering stabiliser for higher speeds and adding some RR300 parts if you want more top end power.
Remember like all bikes these Beta models do have known issues, some of which could cost you a lot of money and/or leave you stranded on the track! See our known issues vid: https://www.youtube.com/watch?v=-TpjNBz0n4A