I don't think I've seen any shoujo-ai series. The closest thing might be Sasameki Koto, but that's still more of a yuri. Are you making a distinction between Yuri and Shoujo-Ai in this question?
looked up Shojo-Ai on Anime News Network, and they indicate that "it has become increasingly popular in North America for shōjo-ai titles to be labelled "yuri," both by fans and distributors." (perhaps a root of my confusion), so I'm just gonna use the definition of non-pornographic girl-girl relationship anime when answering this question.
It's tough to compare Yuru Yuri and Strawberry Panic because I watch them for totally different reasons. Yuru Yuri is the best for a good belly laugh. Strawberry Panic is best to go moe-crazy and for the drama. Overall, I'd pick Yuru Yuri.
i haven't seen this show, but couldn't it be considered shoujo-ai light? isn't one of the girl characters daydreaming about other girl characters or something like that?
I've seen this show, a long time ago, if they did it wasn't because they were in love with them, it would have been for comedy reasons. Lucky Star is pretty much the definition of a school life/slice of life anime
yeah, pinpointing the difference between Shoujo Ai and Yuri can be tricky. I think the "modern" term for Yuri and Shojou Ai are identical, while the "classical" term for Yuri is essentially Shojou Ai Hentai. i prefer to use the "modern" definition for Yuri, because it's such a cute term and I want to use it for shows I watch.