both coil and air can give you a smooth ride, with air you can fine tune it to your weight with a HP pump, with coil you would have to specify what size spring you want, and possibly have a lbs order you a new one if it's too light or heavy, but with a coil if the internal seals rupture you still have the spring keeping the bike up with air your ride is done until you have it rebuilt,
something to think about
live life like a bullet
FAST HARD AND GO OUT WITH A BANG
It depends on how much adjustability you want. With that big ass bike you aren't looking to save weight. If you don't really mess with your shocks a lot, (most people don't) I would go coil. I have air front and back, and it's a pain sometimes. I never had to mess with my coil sprungs.