I'm down on Bumgarner some because he seemed to have lost some speed off his fastball the past year. In 2009 his K/9 dropped to 6.5 and his walk rate almost doubled. He's still a really nice prospect but some shine has come off for me.
As for Mauer, he is awesome but I don't think anyone should expect a repeat of 2009. It all depends on your expectations.
If I pulled the trigger here, it would be on the assumption that LaPorta and Bumgarner, as good as they are, are replaceable and still yet question marks. Mauer unquestionably improves my immediate and usable talent and also my starting lineup, and he comes without learning curves and such.
Also, I've got a decently balanced team, but I could use more HRs from any where to help my slug and K strategy come to fruition. Even at 18-22, that's a big boost from C (I suffered through Iannetta for 2009, and that was no great shakes).
But my AVG is a soft spot with Dunn, Bruce, Uggla, and others around. I lucked out with Dunn this year--not to mention Hanley's batting title--but adding in a batting champion (even in reduced ABs) at C would be sweet, too. That would help balance out my team and give me more shot at winning each week.
I noticed the guy doesn't have a clear set of 19 keepers, and his only shot at a closer is Nunez. With 19 keepers, most of us are keeping 2 closers, so only 7-9 will be available in the restocking draft or fewer if the projected closer is a protected prospect (a la Motte and Perez last year). In all likelihood, that numbers going to go down closer to the draft, too.
I've pitched giving him Kerry Wood & Tazawa in place of Bumgarner. It makes it a 4 for 1 for him, and even though that's a lot of talent for me to give up, I'd have to consider this a win for me.
If he doesn't like that, then I still have the option of giving up Bum. I'm 60% likely to do that.