There is no wrong answer to such a question.I think more people would say wakeboarding is better only because its more visually appealing,and its more fun no matter what level of rider you are, as far a sk8ing goes you are more limited as a beginner(steeper learning curve)once you learn to jump both wakes,it opens up a whole slew of grab variations 180s and so on.
The "better" sport is the one you choose to have the most fun with...