The Vibrocannon is a weapon of fortune. When you get off those precious few well placed shots, you smile as you watch your enemy scoop up handfulls of models with something akin to dispear on his face. He might even weekly mumble something about "why the hell do eldar players whine about not having barrage weapons?" Most battles after that, they attract perverse amounts of firepower. All that makes for a very fun unit, that in most games will do little but perster your enemy. But lets face it. Perstering, teasing, braggin rights, taunts are half the game (these things are also somtimes called psywarfare)
In my book its one of the more fun units, because its potentionally very deadly, but mostly very fun to field. Especially against the one who did the scooping in days past. So i field it when points allow it, but when not, the Falcon allways finds its way to the tabletop somehow. Allways fielding things that are tested and proven powerfull, in combinations long past the point of predictability, in the long run makes for borrng games. Odd weapons like the Vibro, helps keep the game alive and flexible, because they are part of a risktaking and experimenting style of game that is more fun to play, and more fun to play against. Id far sooner loose a close and exiting game, then have a sure win.
The falcon is one of those sure things, and the vibro one of those "what if" things. So in the end it comes down to style, and how badly you want to win.
