My primary selections of Bridge and BlueStar was influenced by their use of the standard Arch repositories and view their relation to Arch as similar to Sabayon's relation to gentoo. I did look at the others you mention but ruled them out due to their customizations and inability to use the original arch repositories. As for pacman, there are several GUIs available that I plan to try out. My inclusion of Mageia was simple curiosity as to how it compares.
Over the years I've used Red Hat (pre fedora) SuSE and openSUSE and tried Ubuntu, CentOS, Knoppix, and a few others I can't remember but since 2006 I've been running Sabayon. With a few exceptions it has done very well. There have been occasional problems like upgrades changing the default kernel or opengl selection but I now make a habit of using eselect to check the opengl, opencl, kernel, and bzimage selected after every upgrade.
The selection of Rigo and elimination of Sulfur was just the latest of a number of disappointing changes to Sabayon. In the past I've reported bugs that were marked 'won't fix', requested package additions that were rejected, and at one point commented on the removal of the ability to select categories in Sulfur and have the packages it contains displayed. I was told to expect that feature to return in a future release but it never did. Now Sulfur itself is gone. Entropy is good, but as I said for large numbers of package updates I like to break it up into groups and the easiest way to do so is via Sulfur.
Why does this matter? I no longer have dsl and currently rely on tethering my unlimited data android phone to my computer. If I get a call or have to make a call downloads are interrupted. It's a bit of an inconvenience to have a large package download interrupted, resume, fail the checks, and re-download. By grouping the downloads I can upgrade a group of smaller packages when interruptions are more likely to happen and do the larger package downloads at night when interruption is unlikely to happen.
Former Sabayon user (2005 - 2013) and current Arch user.
I liked Sabayon until it switched to Rigo and becoming the gentoo equivalent of Ubuntu. Extreme browsing? Extreme gaming? Extreme work? Extreme development? Like, totally gnarly, dude!