Honestly, there are only 2-4 final forms that are noticeably (worse/better) than the rest.

Cheetah is too good.
Walrus is probably too good.
Lemur really kinda sucks now.

....and that's pretty much it. Though I can understand if you don't like Howler Monkey or Giant Wasp because they playstyle doesn't fit.

Zulg did a really really great job balancing the forms. While some might seem "more powerful", I think forms like Cobra, Dire Wolf, Electric Eel are really really nice forms.