The full AKA Retail version will not be tied to your hardware. This means you see free to change the OS to a different system, as long as you have at most 1 system activated with a single product key.
The oem (which are more used by prebuilts) will be tied to your motherboard. This means if you have an oem version installed, you will not be able to upgrade motherboard or change to a different system without buying a new product key.
You generally want the 'Full' version. That said, you can buy the OEM package and just use the product key that comes with it with an ISO downloaded from Microsoft. This will act as a retail version.