Both devices use the Windows operating system. Surface Pro tablet comes with Windows 10, if you want it on your Surface Laptop, then you must upgrade your Windows (for free of course).
Surface Laptop is of course heavier and bigger than the Surface Pro. The later has a long battery life, it uses the same connectivity as the Surface Laptop and the typing experience is pleasant. There is one aspect in which size does matter: the display. The Surface Laptop has a bigger screen: 13.5 inch PixelSense Display.
In term of connectivity, both devices would need more USB and USB-C slots. We still have to use USB extender cables for both devices.
Both machines use an Alcantara keyboard which is very pleasant to use. The Surface Pro device allows you to change the keyboard and you can also use the Surface Pen and Surface Dial. These features are not easy to use with the Surface Laptop. Just imagine yourself trying to write something on your laptop screen with the Surface Pen. It does not lay flat so it is not very convenient.
The Surface Laptop has 128 GB, 256 GB or 512 GB memory options and up to 16 GB of RAM. Its processor is a 7th Generation Intel Core i5 or i7.
The Surface Pro offers 13.5 hours of battery life and different keyboard colors should you get bored of using only one. It comes to 4 GB of RAM and 128 GB of internal memory.
It seems that the choice is between a laptop and a laptop-tablet hybrid. For the more conventional tastes, the Surface Laptop is a clear winner. The more daring technology consumers will for sure want to experience the new Surface Pro. The choice is yours, the battle has just begun.