All "Pros" are in the newer iMacs (Faster processor speed, larger hard drive, more or faster RAM, faster FSB, higher resale value, etc)
All "Cons" are in the older iMacs (Slower processor speed, smaller hard drive, less or slower RAM, slower FSB, lower resale value, etc)
Not true. The older iMac processors are essentially the same as the newer iMacs.
The newer iMacs have a larger hard drive...but cheaper to buy an external hard drive with the money saved from the older iMac).
The newer iMacs have more/faster RAM...but much more expensive than older iMac DDR2 memory and not a noticeable real-world difference from what I've read.
Same deal with FSB...not a significant real-world difference.
Newer iMac has an extra USB port but no longer has FireWire 400.
Newer iMac has a keypad-less keyboard standard (keyboard with keypad is an option). Older iMac has keyboard with keypad standard.
Newer iMac no longer comes with Apple Remote.
All iMacs, even refurbs, come with iLife 09. For refurbs, you have to install iLife 09 yourself from the enclosed CD. Not a big deal.
Because the only diff betw the newer iMac and the older iMac is minor tech specs and not a new technological innovation, the resale values won't differ much. In fact, for those looking for FW400, the older iMac will have just as high a resale value.
Save about $600 for similar configs between new iMac and refurb iMac by buying the older refurb iMac.
I got an older 24" 2.8 refurb iMac for $1199. Use the money I saved for 4GB RAM (only $40), a 1 TB external HD ($100), and pocketed the rest.