Is Windows 10 Pro better off being in SSD or HDD?

[SPLeo27]

I am planning on building a Gaming Desktop. I want to know if i should get Windows 10 Pro on SSD or HDD and how do both drives affect the OS? I am planning to get 1TB (maybe more) HDD and either 250GB or 500GB SSD

 

[alexoiu]

On the SSD, together with the most used programs, for faster access.
Other data/music/movies/photos - on the HDD.

 

[USAFRet]

OS on the SSD. Whether it be Win 7, 8.1, 10....whatever.
The OS goes on an SSD.