I've used both, and prefer the bench capper. It's more versatile, in that it gives a reliable seal on a wide variety of head styles, many of which the two-wing can't handle. YMMV.
Depending on the type of bench capper, it may or may not be better. For some of them, especially the older ones I'm familiar with, it's great if all your bottles are the same height. If you have different height bottles, you'll spend forever and a day adjusting the bloody thing to get it to work. I guess the newer ones are easier to adjust, but it still has to be done.