Besides, those who will buy the game will buy it and those who can't will not buy it no matter what.
Partially true; there are those that will buy it and there are those that would rather try get it for free before resorting to buy it.

HL2 was a prime example: there were many people who bought it, because they could not pirate it before release. Quite a stark contrast to Doom3 which was pirated before it was released. How many of those people who pirated it, went to buy it? Many finished the game before it was even available to buy, so why bother buying it?

Is AC2 fully cracked yet? Does anyone know a "friend of a friend" who has finished the game on the cracked version? Last I heard, they couldn't because DRM was injected in several places causing them to lose their save games etc. Meaning they would still need to download several versions of the crack, before they will eventually finish the game.

If that is the case, then I'd say:
Ubisoft 1
Pirates 0