The spring air series you want for a patriot is the 100 series, either the 101 or if you fly from grass I'd use the 101 HD, same gear but with 3/16" struts instead of 5/32".
They used to make a slimline 100 series as well, but I don't think they were needed for the patriot.
You can get either a belly or firewall mount nose gear in that series.
http://www.retracts.com/Retrax_100.htm
As for benefits of air vs mechanical, there are many IMO.
1. They are easier to set up, you have only one pushrod from a servo to a valve, easy, doesn't have to run a dead straight line, doesn't even have to be a retract servo.
2. Your air valve servo can be a micro servo, saves a large amount of weight over a retract servo
3. In a patriot you save one full servo since you need a retract servo in the wing AND one in the fuse for the nose gear if using mechanicals.
4. There is no chance of a bent gear wire causing a gear to stick in the wheel well and have the servo stall, drain your battery and boom, no more airplane....
Yes it does take up a bit more space if you consider the air tank and fill valves, but they weigh almost nothing so you can mount them where-ever you want to. Generally speaking, mechanical retracts have plastic bodies as well, I have broken many a mechanical retract over the years, never had a problem with air.
The only downside to Spring Air retracts is the wheels don't stay tucked in the wing without air pressure so transport can be a bit of a pain, however, you can retract the gear, put a small 1/8" dowel into the frame to keep the air cylinder from moving and lock them in the up position for transport, just a small bit of extra work.
I definitely prefer air over mechanical
