Advantage of Linux over Solaris
In response to this:
Idle power draw of Fedora 10: 100W
Idle power draw of Opensolaris 2008-11: 135W
Sure, there are other arguments. But with energy prices the way they are, choosing Solaris is choosing to spend significantly more money on your hosting. Remember to factor that into your TCO calculations.
(Testing done on a 4-way AMD with a Radeon X1900 graphics card, which is what I happen to have to hand. Out of the box configuration.)