Why? Well, blame Rich Harden. My own personal over/under on how many starts he makes this year is 11, and I'd take the under. But remember, I'm the same guy who drafted Harden for both his 2006 (9 starts) and 2007 (4 starts) seasons, but not his 2008 (26 starts) season. I'm also the guy who wrote stuff about Alexei and then drafted him in his own draft. So you can certainly take my advice, but remember that I'm pretty biased here.
As for stats, I wouldn't read much into their stats so far this year:
Alexei: 0-3 (1 game)
Hardy: 0-5 (1 game)
Harden: Yet to pitch in regular season, but did give up three HR in each of his last two spring training starts.
I admit that I'd be tempted because of the Hardy/Harden thing. I'd be especially tempted if your team already has both Uptons on it. Then again, if you have both Manny and Alexei Ramirez I'd be less tempted. On a more serious note, Hardy will get some nice stats at the end of the year, but he seems to get most of them in the same week, so I'd personally avoid him if you are in a H2H league.
I'm all over the place. Bottom line? Stick with Sexy Alexei. Harden is a great player when healthy (top ten SP? top five? He's captain of the all-value-per-appearance team), but you'd be taking a big gamble by trading for him. Arguably (and according to ADP, which is meaningless now that the season has started, but still), Alexei is the best player in the deal, and you rarely want to be on the side of the deal that is giving up the best player.
Good luck, Anon!