Well one plus is the total RAM footprint of a Linux distro + a DE, is less (by a lot) than just OS X's kernel. Right now, xnu alone is using 960MB on my laptop. Oink oink oink.
Edit:MBP82, created new user accounts, reboot, login, launch Firefox, load CNN, wait 2 minutes. Did this twice each Fedora 21 Workstation (Gnome) and OS X 10.9.5. Fedora free -m used = 614MB. OS X top PhysMem Used = 2866M, Activity Monitor Memory Used = 3.69GB. I suspect Activity Monitor includes "wired" which top splits out. shrug Anyway, it's not a tiny difference. Omnomnomnom.