In the end Mac wins because it's the only one of the three that can - easily - run both the others. I dualboot OSX and WinXP (even though I never actually use winxp because I can't stand it) and once installed ubuntu on an iMac with little difficulty, although admittedly it did suck because no airport drivers and no ppc graphics drivers.
So, yeah. Get an intel iMac, replace the wireless network card (or plug it in to the ethernets), then install all three and be happy.
Problem: solved.