If you are trying to save $ then buy the Coffman shorty. I have one. Sounds great and was only $230 shipped. I shopped solely on sound quality and didn't care about price. Just lucky that the one that sounded best to me was also the cheapest.
Don't waste your time on slip on. Does not really change sound much at all. Do a full exhaust and you'll get rid of the cat and it will sound like whole different bike plus you will drop about 10-12 lbs weight. Weight means a lot on these small CC bikes.You can do a complete Arrow exhaust for under $700. JMHO.