I consider the sound from the Panels being equal as both had the ability to totally disappear within the music. The biggest difference between the two was the bass reproduction, with the Summit producing top notch bass, while the Vantage was not quite up to the same level as the Summit. Even after some adjustments with the Vantage controls I just did not find it as well define and authoritative - but remember the Vantage has one 8" and the Summit has two 10".
But like I have stated before, for the $5k you will save with the Vantage, you can purchase a ML Sub, or Sub of your choice, and easily augment the bass to your liking. If I had to decide today which to buy, it would probably be the Vantage and use the extra cash saved for other items in the system....music, components, cables, etc.
Dan