I love Rocks. They have done an amazing job with that Distro.
I won't call myself an expert or anything like that, but I /really/
enjoy the clustering world and have been involved with it for a few
years now (both for fun and work). I have worked with clusters across a
wide range of software and hardware as well as with most of the Distro's
you have listed and many more you didn't. I have not found anything like
Rocks; at least not with the cluster work I do/have done.
Most of the Debian based distros I have worked with are good and get the
job done, but none of them quite compare with Rocks in the same way.
It's an apples-to-oranges-but-at-least-they-are-both-fruit comparison at
best. I wish they had a Debian based port... *sigh*
Take my comments for what you may think they are worth. I absolutely
adore Debian for my home and my servers but I have absolutely nothing
but praise for the Rocks team when it comes to clustering.
Just MHO.