Small pneumatics to fire in poor vis and close range are easily dominant. You can load them way faster and they cut through the water like a knife.
You specified small pneumatics but I think that all pneumatics are not faster to load than a band gun as is evident in your video http://www.youtube.com/watch?v=vcDk5LqjVlY Especially if you factor in the time of taking out the loader from wherever your have it stashed and then replacing it.
It is also interesting to note that pneumatics have the potential of firing as you're loading them, this is not possible with band guns. Also the shaft release mechanism on a pneumatic is less secure than a wood gun with a stainless steel mech. It's much more sensitive and can release if the gun sustains an impact. Wear on the pneumatic release mech is not evident unless you take apart the gun.