If you're satisfied, stick with Ubuntu. Sabayon is a good Gentoo-based distro. What that means is that you use Portage to install everything. Gentoo people are all about Portage because everything you install is compiled specifically for your computer, which causes performance increases.
I used Sabayon for a while, and didn't like waiting around for long periods of time to have everything installed. With Portage you have to download the files and their dependencies, wait a very long time for the program and all of its dependencies to compile, then wait for them to be installed. In Ubuntu, you just download the binaries and install them.
When I was using Sabayon, I decided that the unnoticeable performance increase that I got from compiling every app I had on my computer was definitely not worth the extremely long waits I had to install the apps that I wanted. But to each his own.
Other than that, it's not a bad distro. It's a KDE distro and regular Ubuntu is Gnome. So you have to think about your preference there.
I heard that Sabayon is working on having hybrid repos that will let you choose whether you want to install binaries or compile your apps. That's a pretty good move if it works well.
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