I have run both, and I agree with the post above, that it isn't a huge difference.
The biggest change is noticable in first gear. Stock gearing, it would come up slowly in first at wide open. -1 it would come up a little quicker at full throttle. -1/+2 it will come up almost every time above 60-75% throttle.
Either way, it will be ok. I think I'm running right near 7000 rpm at 70 mph with the -1/+2. One thing to consider, is that if you want to save money, you can just purchase a -1 front in the stock 525 size for around $20. If you are going to swap out all of the parts, go with 520, and go ahead and do the -1/+2.
Just an FYI, Kawi uses the same front sprocket design, in case your Suzuki dealership doesn't have one in stock...