Better? Comparing abstract to realism is never a good thing to do. Well, it's not good if you're asking your viewers to choose one artist's talent over the other. It's all how you perceive art.
But if you'd like to go into the different styles:
The goal of
abstract art is to arrange shapes and colors in a way that is aesthetically pleasing, to the human eye. This isn't something artist usually calculate; it's usually something they feel out. There really aren't any rules. You throw something on the canvas, and name it something. Goal complete.
The goal of
realism art is all about form, angles, proportions, etc. being correct; as realistic as possible.
Hitler failed his goal at creating the most realistic piece. Angles and proportions are skewed throughout his painting, while J-M. Basquiat completed his goal. Even though it was a simpler task, Basquiat piece looks the part. Hitler's does not.
Thus, to me, Basquiat painting is superior.