Alex,
I would recommend not to go to 7.10.
So the choice is between 7.20 and 7.30
7.20 exists for a longer time than 7.30.
So we can call it more mature [less chance of a software bug].
7.30 is quite new and introduced a few new features like the gracefull shutdown that everybody was looking for.
But because it is new, we have less information about stability.
I hope this description will help you chose the best image for you.
Gilles.