I think 6 people have misunderstood the question: it's who would you rather have for the rest of the season. What has already been done wouldn't have any affect on the stats you'd get. That means A-Rod's horrible start doesn't negatively affect you, and Rolen's great start doesn't help you.
Take away each player's first month and A-Rod has more HR, R, and SB's than Rolen. And he's pretty close in BA and RBI. So even if Rolen continues at this torrid pace, A-Rod will probably beat him in 3 categories and will be right behind him in the other two. And do you honestly think Rolen will play like this all year? Hell no.
It shouldn't even be a question, and it's A-Rod. If the stats were counted as retroactive, then that's another story, but that's not what the question is.
"Jack, will you call me, if you're able?"
"I've got your phone number written, in the back of my Bible."