I promise I don't mean to cause a war here, but I want to ask why so many people recommend using "enterprise" Linux (specifically Redhat) over something like Ubuntu Lucid. Is this purely for support/warranty purposes, or could somebody give me a list of some key things that make Redhat more suitable (if there are some) (my purposes are for a hosted SAAS platform on the web).
Red Hat is a lot more stable and static compared to Ubuntu. This makes it easy to test, and you can't release software claiming support for an OS without strenuous testing. Software vendors won't officially support an OS they don't offer commercial support for.
That being said, if you're a distro release from around the same time as the targeted Red Hat release, it will probably just work perfectly. I have modified
If you're looking for something FOSS but maintaining guaranteed compatibility with Red Hat, go with CentOS. It's the Red Hat sources, which have to be made available under the GPL, recompiled without the branding and the Red Hat Network support.
If you don't have any software packages to worry about, go with what you're most comfortable with.
ISVs prefer RHEL (and SLES, to be fair). Sometimes they will provide a package for RHEL, but very, very few provide packages for Ubuntu. And they may also provide paid support for only certain distros, RHEL among them.