I don't disagree with your sentiment to wait and see and that it's often better to stick with veterans rather than young players, but Craig is no Chris Duncan. Duncan had a pretty long minor league history of mediocrity that suggested he wouldn't last long if he made it to the majors.I don't think you let Berkman walk at all, you remember when Chris Duncan tore up the league for two seasons? Remember when Ryan Ludwick hit 30 home runs? Even with his aches, Berkman's a safer bet than Craig or Adams and if you can get him back for another 1 year 12M type deal you do it, but I also don't think I'd go two years unless it was a big discount.
Ludwick is a more interesting story because he arrived so late. He hit during his prime years and then stopped -- age 31. Plus, if you throw out his crazy 151 OPS+ season, he was essentially a 105 ops+ hitter with the Cards. No surprise that that kind of guy drops from 104 to 90'ish and below when he crosses 30.
Craig profiled as exactly what he's become -- a power hitter and defensive versatility. He's got staying power and he's pretty close to a known quantity at this point. It will almost certainly be a better use of our resources next year to let a 37 year old Berkman walk and plug Craig or Adams in for him. We'd be better served spending some of our money on a 2b'man and on the rotation... Maybe even let Miller apprentice in the bullpen next year.
If Berkman wants to sign a smaller contract and plan to start 100 games next year splitting time with Craig, then I would be all for it (assuming he plays this season out as we expect). But, i woudn't pay him another $12M to keep Craig on the bench. Odds are high that Craig will outproduce him this season.