It really depends on what you will be doing with it and if you can live with an external optical drive if CD's or DVD's play a major role in your computing in which case a MBP which is as close to a desktop replacement as there is unless of course we are talking Mac Pro.
If you're buying a display to go with it, even an 11" MBA will handle browsing, email, etc... The one thing that you may run into is storage space limitations. That's easily resolved with a simple external hard drive.
As others have mentioned, it would depend on your use. If portability isn't an issue, my recommendation would be go with an IMac. Big beautiful screen, plenty of ports for connecting devices, same cost.
I am a full time student using the MBA as my main / only computer so far and its been great.
If all you really do is do work (run spreadsheets and word documents), swap emails, and casual internet browsing, it should be fine.
If you don't really travel with the laptop though, I don't see why you don't look at the pro or imac first because it has more outlets and the CD drive and more storage space.
OP... if you post back in this thread what you intend to use the computer for you may get some relevant input. Short of that, replies are sort of like shooting in the dark.
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