My iMac G5 is really starting to show its age. I can't decide if I want a 27" iMac or a 13" MacbookAir. I don't really need an optical drive. I use it to import CD's to iTunes. I can always do that on anther Mac and transfer the files later.
There are ALOT more variables in deciding between an iMac 27 inch and a 13 inch MBA apart from CD-Rom drive
one big one is... Do you need mobility or are you usually stationed?