I really like my Delkevic SS70s. Smaller, lighter, not much louder than stock even with the baffles removes, works with luggage, fit and finish was excellent and not terribly expensive. I've had them on since last fall and so far no rusty bits. Even though it's not much louder it's still the whiny in-line 4 rasp.
Other than the visual effect and weight, the biggest advantage I see is it gives much better access to the chain for maintenance and when lining up the rear stand on the spools.
2014 Ninja w/bags, Motowerks lowered pegs, Seth Lamm Seat, Puig screen, Givi XS307 tank bag, WOLO BadBoy horn, LEDPerf H7C HID lights, Aerostitch Roadcrafter