This is based on wanting a headshot, not artistic merit. Headshots tend to be about following industry trends than art. And what little I know about them.
First, I think vertical would be prefered. The crop is a bit tight to the top of his head. From the rectangular highlight, it looks like you might have used a flash attached with a cord and held off to the side. The light is a bit harsh. It's a lot better than on-camera flash, but for an actors headshot, I think more diffuse light would be better accepted by the intended audiance.
The slouch is noticable even in the first one. For a straight on shot, his posture is going to be important. His hair is also blending into the background.
It's good to be different, but when dealing with this industry, you have to be different while being the same. Sounds stupid, I know. You might be able to stretch with one thing, but if you do too many things different from the standard, you tend to get rejected out of hand.
I'm not being critical as far as artistic merits go. I like the second image and think it's a great portrait of him. I'm also no expert. This is just what my exposure has been. I'd look at lots and lots of headshots and try to find a way to make yours look similar while still fitting his style.