It's tough, because of course they're all good and important to the story. Now that we've seen two of each, I lean towards the AU episodes. I think this is for various reasons. For one, I think the novelty of issues and quirks in the AU is more interesting than the stuff we're used to over here. We get to spend time seeing what's different. Also, even though she's being masked right now, our Olivia is still over here, and I'm currently finding her plight the most interesting thing on the show. She's also my favorite character, so I enjoy all her adventures. I also like the dynamic of the Fringe team over there. They're more of a team and they're fun, whereas Over Here we have three characters who're all there to babysit Walter to some degree, and all seem more independent of each other.