I'd say it is like comparing apples to kiwis. You know how a ripe apple is crisp and snaps, that's the Campy. A ripe kiwi is sweet and soft, that's the 105. Both get the same job done but with a different feel and taste.

With that said, I prefer my 1996 Shimano 105SC 8 speed group, over my 2008-9 Campy Centaur/Comp Triple 10 speed group. But not by much.