I like season 5 better. There's so many great stuff from this season... The introduction of Lips (as well as Pops), the best version of the opening (the first version I saw parts of, in The Secrets of the Muppets), the best version of the closing theme (which I'd heard on the Playhouse Video compilations, before I'd seen any actual episodes), Rizzo starts to be used more (after being introduced late in the previous season), Gaffer appears frequently (after being seen twice the previous season), and such great episodes as the ones with Gene Kelly, Loretta Switt, Shirley Bassey, Brooke Shields, Marty Feldman, and Linda Ronstadt.
One of the few things about the last season I see as a fault, but am really just nitpicking about, is that this season seemed to have too many themed episodes and episodes where backstage issues affected the on-stage acts. I don't have a big problem with it, but I feel they could have done a little less with it. But with it being their last season and the fact that the writers initially only thought they'd be able to come up with three years worth of material, I wonder if doing all these theme/gimmicky episodes was a way to help prevent them from running out of ideas.
I've mentioned this a few times recently, but I feel like the fifth season was under-represented in the Playhouse Video compilations. There are a few that heavily feature fifth season material, though it seems the ones with the most season 5 clips have multiple related clips from the same episodes (whether related by backstage plot or multiple clips with the same guest stars). Though I've noticed that some of the videos under-represent other seasons (only two season 1 clips in Rock Music with the Muppets, only two season 4 clips in Muppet Weird Stuff), and by my count at least 19 season 5 episodes are represented in some way over the course of the ten videos. But I wonder if the under-representation is due to many season 5 episodes having so many "connected" segments (which may or may not look weird without other segments or backstage clips).
Though it seems the somewhat limited representation of season 5 on the Playhouse Videos is a lot better than the representation of season 1 on the It's the Muppets and Very Best of The Muppet Show releases. Interestingly, when it comes to sketches that are "connected", the first two volumes of The Very Best of The Muppet Show contain the Vets Hospital and Pigs in Space segments from the Gene Kelly episode. Wouldn't it make more sense to include them both on the same tape, since the Pigs in Space one directly mentions that the announcer fell in Vets Hospital?
But while I like season 5 better, I really want season 4 to come first, as it should (but if they are having trouble clearing rights then by all means release season 5 first!). I've noticed that compared to other seasons season 4 doesn't introduce very many new characters, but it does have many instances of introducing one-shot/rarely-seen characters who are NOT made from whatnot patterns but being their own puppet. So maybe they had planned on putting Geri and the Attrics in more episodes, but it's a little odd they made new puppets for characters like MAMMA (well, thy couldn't make a robot from a whatnot), Angus McGonacle, and the Devil, yet those characters hardly appeared again, I'm not sure if they intended on bringing them back.