Are we so sure they're different? The Posting of the Hunt sounds more like a game, and also not too far off from what happened in Bloodmoon.
Actually, the Posting of the Hunt details events quite different from what we saw in bloodmoon. The daedric Hunt only occurs in a particular place, for example (namely, that level in Battlespire), with the reward being prestige and the ability to draw upon the magical energies enveloping the hunting grounds. The hunt is inaugurated with particular rituals (none of which are seen in bloodmoon), and is governed by a strict set of laws, which designate the methodology of the hunt, the Innocent quarry's right to a means of escape, (traditionally by means of six keys which must be found to activate a teleporter), the use of the spear of Bitter mercy by the Hunstmen, etc. The Ritual of the Hunt also protects the Huntsmen from all damage except for that inflicted by the Spear of Bitter Mercy. Nothing that happened in bloodmoon even resembles that. (edit: oh, and the only time we see the Wild Hunt detailed in the Posting of the Hunt carried out, it's done by servants of Mehrunes Dagon)
Also, the bosmer version is very different, involving the bosmer transforming into wild monsters. It lacks the laws and strictures featured in the Posting of the Hunt. (not to mention it's a mortal affair, whereas the Posting of the Hunt details a Daedric ritual for Daedra)