Well, less plastic feel like and also the key action. Those feel really cheap and bad with the oxygen and a lot better with the novation impulse. But then again, there's a price difference of about 200 euros there.
Mostly you get what you pay for and 100 to 150 euros for a keyboard with 49 keys minimal is not that much for quality on all they put on those keyboards nowadays.
Anyway, that's my two cents, I advice everyone who's looking for a keyboard to go feel it in a shop for themselves!
Obviously Xabiton handles the oxygen just fine and I like his music a lot!
Eventually an el cheapo keyboard very plastic like and all still enables you to make good music if you have that in you. It's just that if you're getting better in time at that instrument, there's a good chance you'll be frustrated with the quality of it and would want a better one, or, with all the difficult things you have to overcome becoming a musician/bedroom producer, you don't want to be hold back by quality issues. Quality issues that could be overcome a lot better by spending a bit more. All depending on what your priorities are, where on the path you are, what your budget is, etc.
You wouldn't see a 30 year professional piano player buying an M-Audio oxygen and on the other hand, you wouldn't see someone just beginning spending about 100 k on a steinway piano either
Man, I'd wish you could become a millionair by just wanting it real bad!