These are some screen caps from the movie, for comparisson.
With the battle mask.
A side shot of the head showing the ears:
I think the original head looks closer to the movie version. The premium is more accurate with the long ears, but the head isn't round enough or big enough to be in scale with the ears like in that second photo. I think the original is more accurate, and I also prefer it over the premium.
(photos are from tfw2005 - http://www.tfw2005.com/transformers-...+Optimus+Prime )