I think LaRoche is your safest bet. He is concistently decent, has some power, and he's been hitting the ball well recently. If your team is in good shape and you want to make sure you just dont screw the pooch, go with LaRoche.
On the other hand, Chris Davis is your high risk/high reward guy. He started off hot when he was called back up last week, but he slumped over the holiday weekend. He might bat .190 with 3 hr's and 800 k's the rest of the way, but he also might hit .260 with 10 homers and 20+ rbi. If you are in 4th or 5th place and you really need to make something happen to get into the money, Davis might be worth the risk. Though risky as hell, Davis has the best chance of replicating the stats you would have gotten from Pena....besides, LoRoche will still be there if Davis craps the bed over the next 7-10 days.
Help with mu similar question? http://www.fantasybaseballcafe.com/forums/viewtopic.php?t=397070