Windows 8.1 Or Windows 7?

Windows 8.1 is a fine OS. I was a hardcore windows 7 fan, and when windows 8 came, I was among the ones who hated it. And I still do. But, I can assure you, that, windows 8.1 is a very good OS. Much better than windows 7. But, down there, it's your own personal preference. The one that you feel more comfortable with.
 
I am doing a new PC build myself and I will be using Win 7 64bit Ultimate. They are still available, I figure that with Win 10 coming out and being a free upgrade stick with 7 and not have to learn 8.1, just 10 when it's released.
 
Windows 7:
End of mainstream support - January 13, 2015
End of extended support - January 14, 2020

Windows 8:
End of mainstream support - January 9, 2018
End of extended support - January 10, 2023

What is the difference between mainstream support and extended support?
Mainstream support—Microsoft will offer mainstream support for a minimum of 5 years from the date of a product's general availability, or for 2 years after the successor product is released, whichever is longer. For example, if you buy a new version of Windows and five years later another version is released, you will still have two years of support left for the previous version.

Extended support—Microsoft will offer extended support for either a minimum of 5 years from the date of a product's general availability, or for 2 years after the second successor product (two versions later) is released, whichever is longer.