On the Membership Sign Up page, show the features of all membership types side-by-side *before* the user clicks the Join button.

Once the user clicks "Join" you currently show a table with the relevant features of the membership. However, for a user to compare memberships, they have to click Join, then go back, click Join for the second membership, then go back etc. They must also write down or remember all the info to make the comparison, which is very cumbersome. A simple solution is to show a comparison table before someone clicks a Join button.