Both are smiling. Both look comfortable, relaxed, like they're having fun.
Wynne's a bit cleaner in her appearance than Harper is; the absence of a tie helps with his relaxed look, but results in more visible rumples in his shirt.
Plus, he's got a small green folder in front of him. This could symbolize nothing; it could imply that his Ontario File is a small one. It also makes him look a bit like a kid at school.
Premier Wynne, however, has a professional folder in front of her. Added to her overall look, she looks more the role of engaged, properly-resourced leader than Harper does.
And they both have Canadian flags behind them.
I can see why Team Harper released this pic, but were I them, I would have framed it differently.