The Microsoft Surface Pro 2 essentially combines both Apple iPad Air and MacBook Air into a single efficient package. Therefore comparing these two tablets side by side isn't quite fair. However we could use this head to head comparison to asses if a Surface Pro 2 could in fact replace an iPad and a MacBook Air as your next purchase or if you prefer Apple's offerings.
The Surface Pro 2 features a 10.6 inch full HD touch display, up to 512GB of internal storage, a 5 megapixel rear camera, a 3.5 megapixel front facing camera for Skype video calls, a full USB 3.0 port, mini DisplayPort and a fourth generation Intel Core i5 processor with up to 8GB of RAM.
The Apple iPad Air features a 9.7 inch Retina Display, up to 128GB of internal storage, a 5 megapixel iSight camera capable of 1080p video capture, a secondary 1.2 megapixel camera for FaceTime video calls and an Apple A7 processor
As you can see the iPad Air has a few advantages such as its higher resolution display, lighter frame and cheaper price. However the higher price of the Surface Pro 2 is justified by its powerful Core i5 processor and RAM. Keep in mind that you will have to own both an iPad and a MacBook Air which retails at $999 in order to match for the Surface Pro 2 offers in functionality.
You can read a detailed comparison between the Apple iPad Air and the Microsoft Surface Pro 2 on PhoneArena.