to shoot Arial footage??? Helicopter???

If you're looking for helicopter-shot footage, unless you've got an EXCELLENT pilot in a 4 or 5 blade, forget trying to hand hold with any quality of output.
Generally these days, you're using a gimbal system out of the bottom of the chopper monitored/controlled from inside the aircraft. Sony F700/900/950 are the common cams for this sort of work, be prepared to spend a lot of cash.

I'd think a smaller camera like the A1 would work best. Unless you can shoot out of the side of an open door, the space inside a helicopter or small plane is very cramped, which makes shoulder-mounted or even FX1/VX2100 sized cameras difficult to use, let alone keep steady.

Douglas is right though - without an external gyro stabilizer it is nearly impossible to get good, steady footage from the air. There is a lot of vibration on the frame of the aircraft that makes supporting the camera on anything inside a bad option. You have to make your arms and upper body act like a stabilizer, not resting them against anything in the aircraft, so as to cushion the camera from the aircraft's movements as much as possible - but this is usually a futile effort. I have yet to get any usable footage from the air, and a gyro-stabilized camera's price eliminates it for me.

I've tried the A1, Z1, and V1 from 206's (LongRanger), 600n and on both aircraft, I struggled, but got reasonable footage with a Bogen FigRig with bungie, and it works, sorta. I've gotten decent handheld with mid zoom when strapped in good with a great pilot. But the gyro/gimbal systems are simply the bomb. At 3K an hour plus cam....not cheap, either.

One idea we've talked about is that hot air ballons would be great for these types of shots. We've often talked about getting in on balloon festivals to get the aerials we want of city skylines, etc. You could use any cam you wanted there.

Of course there are obvious issues like you only have one chance per ride to get the shot, you have to wait for the balloon launch dates, will there even be a balloon launch at the location, etc. But it would definately be a cheaper alternative to a gyro.

I had the opportunity to shoot wildlife and scenic footage from a hot air balloon this summer in Kenya.

If it's an option in terms of location, it's a very viable alternative to fixed and rotor wing. I shot using an A1 freehand and on a spiderbace with very favourable results. The effects of wind and convection off the Serengeti were dampened by the balloon to the point of being non-existent.