I was actually going to recommend a CBR 600 of some sort, but before doing that...why don't you give us some idea as to what your budget is, and intended riding is going to be like?
Do you live near twisty roads, or are you commuting in Florida? It makes a huge difference.
You might want a sport bike, however, you might want something a little more "universal." Not talking Harley's here, but if you're using the bike as a commuter, you might be better served by something like a Yamaha FJ600, or FZ6, or similar.
The new Ninja 300 is a HUGE improvement over the 250 (which is still a good bike).
Another bike to consider is a Ducati Monster 620. Super fun little bike, with surprisingly decent power, great sound, awesome brakes AND a slipper clutch! Cost of ownership is a little higher, but it's a unique little bike that is no longer depreciating. I've spent some time on one, and would often pick that bike over much faster and more macho bikes. The thing is a ball of fun.
Otherwise, I would go more towards the CBR vs the GSXR mostly for comfort and quality. You're talking about ten year old bikes, which means that long term quality is going to be an issue...and Honda is the best. Make no mistake, GSXR's are great bikes, and an older GSXR will outperform an older CBR on the racetrack...but that's not where you're riding, is it?