I think I would rather have just one of them done to perfection over both of them done pretty good. I would prefer TB - But if it comes down to it, I would rather have a fully fleshed out RTwP with no TB system if having both made it seem like corners were cut. I just want it to be good, either way, really. I'm already a bit worried about when Swen mentioned something like, 'In D&D you miss a lot if the dice are bad. That doesn't work well in video games.'
If the video game is based on D&D, then it works exactly how it's supposed to. TB or RTwP debate worries me much less than his statement. Tweak around the edges how you like, but at least leave a setting in game to give the option to have core rules complete with random dice rolls. What's the point of even getting the license from WOTC if you're not going to make a game with D&D rules?