This year our team used a 2-segmented arm where the 1st part "tower" is attached to the chassis and the 2nd piece is rotated using the globe motor.
Now by air lines i'm guessing u mean pneumatics? well, we didnt use pneumatics this year but on our '05 robot we did. Then, we had a 3-segmented arm where the second piece was elevated by a large pneumatic piston, then the third section was rotated using the van-door motor (we didn't get that this year
). The thing with pneumatics is that they can only go fully open or fully closed, there is no middle ground like with hydrolics. So if u only want your arm to go to a certain position then pneumatics would work but otherwise i'd go with motors. Also pneumatics are heavy (u got the compressor, all of the regulators, hose, at least 1 tank, and then the pistons) so you'll need keep that in mind as well.