Walril gets my vote because he's actually depicting a scene, whereas Paintingfire's doesn't have much of interest there, except the novelty of the period costume variations of the Avengers. The problem with Walril's piece is that the way the arena is depicted makes it seem very small, barely large enough to encompass the seemingly giant rhino-gladiator. The wall looks like it merely a couple of meters away from him, but then the crowd is depicted as being very far away, and this combination makes it look like the people in the crowd a very very small indeed.
The background in Paintingfire's gives me the impression that he was trying to go for that old medieval illustration style, such as you would find in old bible's, but the shadows belie that notion.
Walril gets the vote.