I started with the following 14 Firefox tabs in two windows:
Astute readers may note that I'm still reading some of the same articles that I was yesterday :-)
I then transfered all of the tabs in the first Firefox window to Chrome, so that I had five Firefox tabs in one window, nine Chrome tabs in one window, and the situation looked like this:
I had to re-sort the processes by name since there were so many chrome processes to keep track of.
Surprisingly memory usage went up. If you add the chrome processes together (and for some reason there are 12 of them for nine tabs) they come to 282MB - more than Firefox had with 14 tabs.
When I moved the remaining Firefox tabs to a new window of Chrome, I got this:
What was previously 280MB in 14 Firefox processes was now 374MB in Chrome, or a 1/3 increase.
Firefox 1, Chrome 0.