imac or macbook air? or sony?

I have the Sony TZ90 and it is small and light. It fits in my purse and it comes with an internal dvd-r. I'm not sure if the macbook does. I'd recommend it. Plus the screen is so crisp and clear. On the outside you can boot straight into dvd mode and use it as a dvd player to watch movies or whatever without booting into windows.
 
It all depends on what you are using it for. If it is going to sit on your desk, an iMac is the right choice. If you are going to want to take it with you everywhere, a MacBook is a better choice. A MacBook Air is a great computer, but you should only purchase if there is another computer in the house that you can wirelessly connect to so you can easily install software and do backups. The regular MacBooks are indeed more powerful, as well as cheaper, than the MacBook Air, though I will be buying an Air myself this year to complement my other Macs.