I liked the vertical design because it's more adaptable and has room to grow. There's basically infinite room to list things underneath, but space on the side is limited, especially for people with lower resolutions and smaller monitors. For example, you want to add the monster type as teh suggested or the xp a player gains at the same level like I think you said. In the vertical design you can just insert additional rows and it will extend the table vertically. If you do that in the horizontal version you would insert additional columns which would squish the whole thing together horizontally.
As far as the black on gray goes, that's easy enough to change, but I find it to be less of a strain on my eyes than black on white.
