Windows 10 product cd key.vs product id key, which is the most important one?

[Larry Amato]

Windows 10 product cd key..vs product id key

I have Widows 10 installed on two laptops..
One was upgraded from win 8.1
the other was from win 7sp 1

The product .. cd keys.. are the same ..except for the product id keys..

Is there a conflict on which is a valid id..is this a normal occurrence..??
Which key is the most important one..??