Here's a photo montage I whipped up in black & white, showing Hunter and Shatner. Now, believe it or not, it's hard to find photos of Shatner smiling in black & white, but very easy to do so with Hunter! This works against the point I was trying to make. But even here, you can see how Shatner's face is softer compared to Hunter, even without smiling much.
These smiling pics of Jeffrey Hunter are the reason that, far more than original model Fred MacMurray, I see Hunter as a live action Captain Marvel. If only, in another world...