$2/4 vs. $3/6? Educate me

When playing live, I always do $2/4 when playing limit games. Tonight I'm going to Atlantic City, and I'm thinking of trying some $3/6 limit, which I've never done before.

I'm wondering what info I should know about ahead of time (e.g. differeneces in rake structure).

I'm also wondering how the players differ between the two limits, if there is an noticeable difference.

Thanks!