The way i see it, the "noobtube" is a lot easier to use than the Barret rifle. Hence the name "noobtube."
Noobtube - Moderate reload time, slow-med shot, faster fire interval than the barret (if i recall correctly), Cheap power, large bullet size, flat out annoying.
However...
Barret Rifle - Moderate reload time, very fast shot, slow shot interval, harder to hit the target due to smaller bullet.
-Dunce