After seeing your bike (but, not the 250), I'd say if the 250 is stock and in good condition, make the trade.
When learning to ride, a bike you can rely on is worth far more than one that's going to need lots of work to stay reliable and pleasant.
I love the 550, btw. But, modified bikes can be a real pain to make into a daily street driver, if the mods aren't done well. Yours looks like it was one done primarily for looks, and a profitable sale, rather than street reliability. And with no fenders/splash guards, riding in anything other than really nice weather is going to be a miserable experience, unless a full body condom is your style.
Cheers,