I'm in love with the 360 as a platform. But there are several reasons I went with PC. There are many reasons I won't go with the 360, in order of whenever I think of them:
1. The 360, for me, is a community machine. Adventure games, as a contrast to this, are very single-player, very personal endeavors. The infrastructure of Live does not benefit an Adventure game in any way, really.
2. I already have all my Telltale games in one folder, and I like that. Keeping it all in the same place is somewhat of an incentive of mine.
3. The subscription model really works for me. I like to pay one flat fee and then feel like I'm getting the benefit of this every time a game comes out. I like just snagging the game without entering payment information or getting a per-game charge.
4. The hard copy with DVD extras at the end of the season is definitely a plus for me. This is an extremely big thing, actually. The disc is a major incentive for me, and I really enjoy it.
5. Point and click adventures are native to the PC. They work best with the maniplation of a mouse or something that replicates that(Wiimote, laptop touchpad). With no such manipulation tool for the 360, I feel I might get frustrated with those controls.
6. Telltale's terms are just great. A more than reasonable amount of downloads, customer service that time and time again goes beyond excellence, and I suppose I include the set-up for subscriptions where the new episodes are automatically dropped into your "collection". The guys and gals at Telltale have proven that they have digital distribution down. At least, through their own hub.
That's really all I can think of for now, really.