In case you're playing catch-up here, the Surface 3 is a transforming 2-in-1. The device itself is a touchscreen tablet, but you can snap on its keyboard cover (and pop out its kickstand) to turn it into a laptop.

The MacBook Air is a traditional (non-touch) laptop.

The older non-"Pro" Surfaces ran the (now more or less defunct) Windows RT, which couldn't run traditional Windows desktop apps (Modern UI Windows Store apps only). But this one does run x86 apps.

The new Surface 3 is 3 percent shorter and 11 percent narrower than the 11-in MacBook Air.

The above spec lists the Surface 3's thickness without its keyboard attached. But when you attach the cover and fold it over (equivalent to how the MacBook is measured), it jumps up to 13.6 mmm (0.54-in).