Yeah, they're just more entertaining. AEG's use an electric motor, some gears, and a piston and cylinder. So no moving bolt, and a whining noise mixed mixed with a 'ka-thunk ka-thunk ka-thunk' rather than a 'rat a tat tat' and such.
Cheap AEG's are going to have crap gearboxes. The parts are often okay, but the tolerances are atrocious. It really pays to be able to work on them and get them functioning buttery-smooth.
A lot of the people who start upgrading the stuff end up just breaking it. Then they complain about how terrible the gun and the expensive parts they bought are. Meanwhile, I have some $100 guns that run like fucking sewing machines and have never had a failure.
There's really not much work to be done gas guns, in comparison. not much you CAN do, besides upgrading the barrels. I highly, highly recommend barrel upgrades. The difference between a stock barrel and a 6.01-6.03mm barrel is astounding. Even in a pistol with a 3-4" barrel, stock to 6.03 makes it like a laser. 'Green gas' is pretty cheap. Propane (same damn thing, although it's stored at a little higher pressure in regular propane tanks) is stupid cheap. But it smells like farts and you shouldn't really use it indoors, regardless.