I think I prefer magical transformations to genetic transformations because it's easier for my brain to hand wave away things like mass difference and other potential physical impossibilities*. I've always worried about what would happen if a pregnant swan maiden changed from human form to swan form.

Having accepted that a werebeast can change form I don't really get annoyed if the were form retains the thought processes and abilities of it's other form - it's already magic, so why not? Telepathy sometimes feels like a convenient get-out clause in a story. It's often more interesting if the cat/dog/reindeer retains human thought processes but has trouble communicating while in the were form.

The thing that does throw me out of a story a bit is clothing. Character transforms to werelizard, scuttles off and does it thing. Character transforms back to human and is fully clothed again. This only just works for me if it's a magical transformation and I still wonder if there's come kind of vast shared portal wardrobe space where all these were creatures leave their clothes to be picked up at the other end of their transformation.

*There is also a bit of my brain that is willing to deal with comic book genetic transformations with "None of the rest of the science here makes sense, so why should this?"