Have you tried asking this quesion on the Xcart forums?
OH WAIT, they wont let you until you buy it, then when you do ask, they will delete your post for “talking about the competition”.
All of these “X or CS-Cart” questions appearing are similiar to entering a store selling only Microsoft products and ask them. “Hey, should I buy Microsoft Office or download Openoffice for free?” Or goto a Linux forum and ask. “Should I use Linux or Windows for my server?”
It gets really one-sided. And you will only get one-way responses asking these types of questions.
I have not seen anyone vouch for X-Cart or any other cart. Well, why would we, since we decided to use this one?
You got to ask yourself. What turns YOU on? Your fetish may not be for everyone. Then decide what to spend your money on.
I use CS-Cart because it’s cr*p, you go ahead and purchase something else. 
As for a benchmark comparison. I don’t think anyone made one.