Honestly, to be fair you have to look at injury and performance. From the performance history standpoint the edge goes to Rolen to continue posting his current numbers for the rest of the year. But he has an injury history that is chronic. His back isn't magically better at age 35 just because he's a Red.
In EE's favor is youth and an interesting upward trend of his numbers. No one thinks his glove is ever going to be adequate, but the minute he was declared healthy, he was put back in the starting lineup and at 3B.
EE may be on a ridiculous hot streak right now, but he's got 3 fewer HR's than Rolen in 80 fewer AB's. He's 7 for his last 19, with 6 of those being HR's. That's an amazing week for any player. For a lot of us, EE's bat was never the problem.
So, if Stewarts early struggles were just that, struggles, (a temporary thing) and EE is healthy, then I'd say Toronto got exactly what they wanted out of the trade.