I am a Gnu/Debian fan for many reasons, including the package management tools. Unfortunately, the existing packages are for version 5.0 so one can not simply apt-get install openerp-server.
The best guide I found is at http://www.theopensourcerer.com/2011/04/19/how-to-install-openerp-6-on-ubuntu-10-04-lts-server-part-1/
It worked just fine for me, including the part 2 for ssl config.
Since you will be installing from source, I think the correct answer to your question is which ever distro you are most comfortable with.
And of course, make sure your review the install docs: http://doc.openerp.com/v6.0/install/linux/index.html