I think it's important to point out something that hasn't been mentioned yet.
The Astros also got Miguel Ascensio. That's Miguel Ascensio AND Jason Jennings for two prospects and an overrated Tavares.
The only way the Astros can come out close to even is if they sign Jennings to a reasonable extension. Forget whether or not Hirsh or Buchholz will be as good as or better than Jennings. Have you seen the FA market for mediocre pitchers? Jennings would have gotten the 5/55 that Meche got if he was on the open market. Unless the 'Stros extend Jennings for a reasonable amount (which isn't 11/m a year), why give up those years of cheap pitching from Hirsh and Buchholz regardless of performance?
I'd rather pay Hirsh and Buchholz a combined 15-20 million (rough estimate) over six years to be mediocre or slightly above than pay Jennings 5.5 million for one year to be good or 50 million for five years to be mediocre or slightly above.
I hope I didn't confuse you, but I think you know what I'm getting at. Unproven or not, I would definitely rather have the Rox side of this deal at this point.