I'm going through the same dilemma but I'd stay away from ebay unless you don't mind replacing them later.
I have some Wildcat's I picked up for cheap but it was just the interior and nav lights so I'm trying to decide if I want the Supernova or Wildcat to finish it out.
Wildcat seems to have done more research but is a smaller company that has had some bumps in the road for delivery...probably grew too fast. They may have been the first on the scene to make lights for our application. Supernova does have bigger switches and better "looking" products. I've heard guys talk about the wire diameter and the apparent quality of the wire but I'm not sure the diameter and color makes it a better product. I do like that they use 3M adhesive strips and the product seems a bit more 'finished'.
Mariner Sails has the Supernova in stock and some older Wildcat stock that you can see to compare.
Dont wildcat and supernova have a guarantee? Thats a big deal to me when im buying new and cant decide. Mariner sails has always stood by their products. Call em up and pick their brains. That might help u make a better decision.