I have a 3 inch PVC one that I use and love it. I have found more gold with it than a shovel in the streams. You can dig a pretty good sized hole with one and be pretty precise with it as well.
For a hand tool. You can move quite a bit of material. And since its a hand tool, there are no regs on them.
they are great for getting stuff out of under water cracks in bedrock, pot holes in bedrock, skim bar panning and for use in micro creeks that you cant a small dredge in.
I feel the are more effective than backpack dredges and need no gas, they are light, and quiet!
I would recommend also useing a shovel as well with it, that way you can pry rocks and pull up the rocks that fall into the bottom of your hole that are too big to get with hand suction.
As far as are any better than others. It does not matter, it will give you an edge in sample testing in areas that you otherwise cant move as much material with.
It gives you more precision, and more volume to move, Both very important when prospecting.