I wouldn't be looking at doing such a setup without Oracle's support contract waiting on the other end of the phone. For that kind of setup, it sounds like you want Oracle support available to help with setup and ongoing needs. If you stick with RHEL your also looking at a support contract from Red Hat which will include your ongoing updates.
From my last server buy, support means your looking at RHEL or SLES (Suse Linux Enterprise Server). HP also recognizes Debian though IBM and Dell did not at that time. RHEL and SLES are the two known for enterprise support with RHEL being the more stable choice; Red Hat didn't just get baught and has made a business of supporting enterprises.
If you really wanted to go it alone, you can look at CentOS. This is basically Red Hat's distribution with the branding stripped out. You won't get Red Hat's support but you will get CenOS updates without an annual support fee.
My guess is that Oracle will soon have a full database stack available also; Spark hardware, Solaris OS, Oracle DB.
In terms of "was inherrently simple to use", it does depend on the distribution. The distribution is the product; "Linux" is just a component along with the rest of the lego pieces. Each distribution does things a little different; be it target customer, configuration choices, ideology or whatnot. "simple to use" generally refers to one of the new user friendly distributions like Ubuntu/Kubuntu, Mandriva, PCLinuxOS and such. Once you focus on the distribution as the product rather than what kernel it happens to run, things become more clear.
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