Ok Joe, no real advantage huh? It's the OS! No pop ups, no viruses, no spyware. What software are you talking about anyhow. This is a graphics dept not a gaming arcade. MS Office suite is totally cross platform to.
What about built in software. The mac comes with iPhoto, iDVD, iTunes, iChat complete with audio and video, It's own browser and mail app without worm holes.
It has finder level features that Longhorn is still dreaming about. The new Mac OS had been rated the best out there my even pc magazines.
Yes, you can beat the price, but your building them for pete's sake. Most of us would rather work with our desktops, not on them. I did however take my 5 year old G4 500 and stick a 1.3 gig processor in it and another 712 mb of Ram. It was a 10 minute job and I've never done it before. If your comparing feature to feature on a Dell and a Mac you won't find the prices that far off and if your hitting the high end systems the Mac will usually be less expensive.
Check it out
http://www.linuxinsider.com/story/But-Macs-Are-Slower-Right-36964.html