IMO Air is more reliable but the downside is you have to have a tank and an onboard air compressor.
I have never ran an electric solenoid type of shifter
You don't need a compressor on the bike, just an air tank.
you will have to have a compressor somewhere if you plan to run air.
if you dont want the compressor look at the co2 kits.
cycletek can tailor his kits to fit your need as well. if you have a quick shifter you wont need the kill box or use that part of the harness.
if you run nitrous you can also run the shifter off the bottle
Do an air shifter if your going to drag race. It is pointless to get a quick shifter because you still have to get your feet up and in position to put pressure on the shifter. Which IMO is the main reason to get an air shifter. Look into a cycletek kit. Matt has great customer service and a quality product. I've had mine for 2 years now and not a single problem from it.
My friends use refillable "airtanks" aka CO2 bottles, it's the same kind used for paintball guns and lasts a long time, hundreds of shifts.