WreckWriter, I agree, competition guns are long, band guns, usually wood. The reason is simple. They are almost silent and with the long shaft, they have long range. The longer the spear is more accurate and has a lot of mass for penetration. In order to load a pneumatic gun, you have to have sufficient reach and sufficient strength to overcome the considerable preload on the piston. Band guns allow for better reach and longer shafts. There is often an intermediate position the band can be cocked to before placing the elastic at it greatest extention and power.
Pneumatic guns of long length must be loaded with one hand on the spearhead with a loader and the other supporting the barrel. You cannot two hand the spear into the barrel. A power selector switch helps, but it doesn't do a thing when you first start to load the gun if it has been discharged on full power. If you manage to pull the spear back, on the low power setting, you can back off and start again with less force--until you get to the point you left of at during your first attempt to load.
Nemrod used to make a gun which had a power lever that could be used to compress the air AFTER cocking. It was a bear to load.
Pneumatic guns have more moving parts and if a seal breaks, your done for the day. Band guns will usually fail at the elastic and that can be changed on the boat. Band guns on the otherhand are just about guaranteed to have a band failure...pneumatics can go 2-3 years between failures. If you have ever seen anyone who has been unlucky enough to be loading or unloading a band gun when the elastic breaks, you know that it can make for a severe injury. The wire attached to the elastic is going to be pulled through one hand or the other when the elastic breaks--nasty. One manufacturer uses kevlar line instead of steel wire. It's quieter and probably safer--although I bet it's gonna hurt if your handling the elastic when it breaks.
For all its, disadvantages, a pneumatic gun can be loaded more quickly than a band gun. You don't have to position the elastics over the shaft first and then string the line. A pneumatic gun shoots almost like a pistol. It goes exactly where you aim it. Many band guns have a slight over or under shoot depending on how precisely the elastics line up with the centerline of the shaft. If you overpower a band gun it becomes inaccurate. Pneumatic guns can be "hip shot" they are so accurate. You don't have to look over the gun to aim. It's much like point shooting with a pistol--you don't actually aim, you simply know where it will impact.
So, all in all, yes, a long band gun is for competition but a pneumatic is great for small spaces and quick shots. I just happen to like pneumatics for their accuracy but they are noisy if the spear doesn't hit the target within the length of the spear...otherwise, the piston impacts the front of the barrel and makes a "smack" which is quite loud.
Some people swear by pneumatics and some by band guns. It's a personal preference.
Larry Stein