I still haven't decided and voted yet...
Old head: designed and sculpted with the body together at the early stage of movie production. Transformation constraints and later changes to the CGI model = body not movie accurate anyway. The head suits the blocky body well, kind of a uniform feel?
New Premium head: obviously intended as an attempt to look more movie accurate. But the ears "feel" too long? Haven't got a toy in hand to help make up my mind yet.
This feels actually kind of like original G1 Prime head vs iPod Prime head.
The iPod Prime head which is modelled after the MP head is more cartoon accurate. But the original head on the original body just feels so right. There's a nostalgic factor at work. Very hard to be objective based on look alone. But this is very different from the movie head situation, because the movie heads are still so new.