It's not just about the bats-- gloves matter now.
Neither Votto nor Alonso are good enough in left field for a guy at first base to OPS 850. If you're going to take that defensive hit, you'll need a guy at 1B to OPS in the 900+ range.
So far, Alonso hasn't shown an ability to do that. His career minor league OPS is 837. He's got a marathon in front of him that he needs to run. He's just begun limbering up and some are insisting he's going to win the race.
Let's see him run first.