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First thing to know is that macbook air is just like a netbook while macbook pro is a fully efficient laptop fully equipped with every thing used for daily computing, so in order to get utmost benefit from your investment my strong recommendation is to buy a macbook pro, the model i will suggest is Apple MacBook Pro MD313LL/A which is the latest 2011 version of macbook pro, and yes yes both will be fully compatible with future version of snow leopard, i think about 5 months ago apple has released latest version of operating system for its mac computers, ios5 is for ipod and ipad

To learn more about the latest macbook pro i suggest you to read this customer review;

http://www.amazon.com/review/R1Z7IETD5KV1DI/ref=cm...

Check it out here, available at nice discount i found;

http://www.amazon.com/Apple-MacBook-MD313LL-13-3-I...

The new MacBook Airs feature the same 1333MHz DDR3 RAM as the MacBook Pro line, though the cheapest 11-inch MacBook Air only features 2GB, while all the other MacBook Air models match the MacBook Pros by having 4GB as standard.

The 11-inch MacBook Air is stated to offer up to five hours of battery life in real-word use, while the 13-inch MacBook and all of the MacBook Pro models are stated to offer up to seven hours of use.

The new MacBook Airs feature two USB 2.0 ports, a headphone port, an SD card slot and a Thunderbolt port. This enables them to connect to the new Thunderbolt Display to add more I/O options.The 13-inch and 15-inch MacBook Pros both have two USB 2.0 ports, a FireWire 800 port, Gigabit Ethernet, an audio line-out an SD card slot and a Thunderbolt port

Either will be fine for your needs. The Pro offers more versatility. The Air is light and compact. Both provide USB connectivity. The Air does not have a DVD/CD drive.

"am I able to upgrade its software"

Yes. The Mac OS comes with a built in App Store from where you can download a new version of Mac OS X. Routines updates to the system are obtained from the built in Software Update application.

Definitely MacBook Pro for schoolwork and general use. They're much more hard wearing and a MacBook air has limits- eg. no usb ports