The iPad Pro's $170 Smart Keyboard is like an oversized iPad Smart Cover. The Smart Keyboard can double as a stand for your monster 12.9-inch-screen tablet and, when folded, a perfect keyboard.
The Smart Keyboard connects magnetically to the iPad Pro via a strip of three metal contacts called a Smart Connector port. The Smart Connector powers the keyboard and acts as a data port, allowing the keyboard to run independent of Bluetooth.
The Surface Pro 3's keyboard is $130 extra. But the Surface Keyboard Cover, as Microsoft calls it, clips onto the Surface tablet using magnets and links via a Bluetooth connection. That differs from the iPad Pro’s keyboard, which has dedicated rock-solid data connection that can't be broken.
The biggest difference between the two (without testing them) is Apple’s Smart Keyboard is a full QWERTY layout, with no numeric keypad. Microsoft’s keyboard is slightly smaller and also does not include a numeric keypad.