WTH, a ruger vs smith debate in the semi-automatic forum? And no-one's mentioned a Glock yet? Wow, what happened?
All kidding aside, I suggest going and holding the weapons you are considering. I don't own either, but when I was shopping around last time, I felt that the Ruger with the mag extension felt "wobbly" for a lack of a better word, and just generally uncomfortable. See how they hold, and then make your decision.