If you get a 250, you're insuring, taxing, and running a 250. If you get a restricted 600, you're insuring, taxing, and running a 600. But it only has 33bhp, so goes no quicker than the 250. Direct Access, we've discovered, doesn't suit everyone. When I was younger, the test was done on a 250, then later a 125. Most people didn't jump up to a 600 as their first bike. If they did, it wouldn't have been comparable to a new 600 anyway. Most people stepped up gradually, as they got used to each new bike. Most people now, see DAS as the only way to go. It's not the case, and you shouldn't be pressured one way or the other. You should do what feels right for you. But coming back to the original question, I'd go for a Ninja 250 or Honda CBR250 or Yamaha YBR250 (if you can find one).