Solaris vs. Redhat
Bill Vass collected the informations for a good comparison sheet in regard of Solaris and Redhat Enterprise Linux . Feel free to leave a comment at Bill´s blog entry when you think there is something incorrect.
By the way, he gives a good explanation why it took so long to opensource Solaris:
That all changed about 2001, and we started internally on the path of open sourcing Solaris, and then later, embraced it all the way across all our products. It took over 5 years to open source Solaris because we had to indemnify every line of code (prove that we wrote it) and / or pay off the companies we licensed it from (we paid out over $200M to make that happen with Solaris).