I was thinking of this earlier today, and I think the big difference is the level of detail on the headsculpts.
He-Man still looked like the original He-Man. The difference was that the details in the sculpt were sharper, and the proportions were more realistic. In a nutshell, things like the eyes were more detailed and realistic, and his head wasn't as squat and cartoony.
In Clawful's case, the facial features are left pretty simplified. Don't get me wrong - it's still a cool figure, and much improved on the original. Some of the details are indeed sharper, but I think the main problem is the design of his eyes. Big, googly eyes with black dots for irises look cartoony, there's no two ways about it.
They added detail and made He-Man's eyes look a lot more realistic. Granted, that may be a bit more challenging with an alien/monster type character, but it's not like the 4H haven't been able to do that before.
But cartoony or not....He's been upgraded and matches the original figure,like the rest of the line...thats what I Love about this line because I feel like a kid again(brings back the memories)....Trap Jaw has yellow eyes with a dot eye and looks great plus he looks just like his original figure and so does Clawful = Perfect!