On one hand, it's (usually) the first thing that a potential reader sees, and having a juicy sexy expertly shaded and detailed cover might prompt a curious click.
On the other hand, it will not represent the actual art quality (and the style) of the comic itself since you didn't draw it, which can cause a feeling of bait-and-switch disappointment in the reader, potentially turning them away.
On the third hand, comic covers being significantly more artful than comic pages is nothing unusual in the printed comic industry, for exactly the reasons in the first hand.
So I'm somewhat divided by this idea. Thoughts?