Nope, there is no such site to my knowledge, and I did try to find one. The best I found is an article written by Renae Haddadin of Quilts On The Corner. Look near the bottom right on this page to find it:
http://quiltsonthecorner.com/
I think the options on quilting machines are too many, changing too rapidly, and too diverse for anyone to actually list and compare them comprehensively. And who would be able to do that objectively? An option that one person thinks is silly is a necessity to someone else.
In many cases, it's not an option that's important, but how the machine is built. For instance, the frame on the Innova Pro Frame is designed with a 4-pole system so that you don't ever have to adjust any poles as you roll your quilt. I didn't even realize that was a benefit until I watched someone with a Gammil using a measuring device to change the height of the poles as she rolled her quilt. I think there are probably many more examples.
Prices also are all over the place, depending on the set of options. I think the only way is to go to shows, try out as many machines as you can, talk to other owners, and join yahoo groups that discuss each machine. (I've heard that some groups won't let you join unless you are an owner, but others welcome people who just want to learn about the machine.) No matter which machine it is, there will be some people with bad experiences, and hopefully many more with good ones. The real test is how the people who are having a bad experience are being treated by the company supporting the machine.
Just for the record, I own an Innova and am very glad I bought it, but I realize it's not the only machine out there, and many people are very happy with other brands.