The suspension is fine. It's not as adjustable as a bespoke sportbike, but it will keep you on the road at a good clip, especially with sticky tires like Michelin Pilot Powers.
The 599 is a more rev-happy bike, with almost as much overall power as the 919. The 919 is turned, as I mentioned, for more torque. Whether you prefer the 19 or the 99 depends on what you like in a bike.
I can't really compare the 919 to any other naked bikes, but if you're looking for a relatively lightweight standard it will be a good choice.