Another close call. Hmmm.
"More Tribbles" has big shoes to fill as a follow-up.
Not as good as the original or as good as it could have been, but it didn't suck as a sequel. ST has done worse follow-ups. And it's just fun to see Kirk and tribbles and Jones and Klingons again.
"Ambergris" I like. Is it too silly with Kirk and Spock having gills and scales and becoming water-breathers? No more than Barclay becoming a spider and Janeway a salamander and Geordi a UV invisible-whatever.
Big points for pushing the envelope showing a waterworld and an aquashuttle and aquatic civilization (or should that be a marine civilization?) This eps has an epic scale, befitting the animation medium. And the story is fairly good, also.
If I must choose, I choose "Ambergris".