Windows 10 hasn't actually been released yet, so it would be difficult for anyone to say.
The preview build is available to those in the Windows Insider Program (Windows Beta testing)
The preview build is very much that - it's unreliable at the moment, and not particularly efficient.
For gaming, use Windows 8.1. Windows 10 is a free upgrade, so when the official one is released, you can install it if you choose to do so.
Hope this helps
Adam