Neither. A System Image from within Windows is wiped out during this process.
Create a full drive image with one of the current Imaging tools.
Macrium Reflect, for instance.
Create this Image on some other physical drive, and have it disconnected during this process.
Also, copy all your personal data off to that other drive as well.
This allows a simple copy to the new OS.
Generally, an in place upgrade from Win 7 to Win 10 works just fine. All your stuff remains.
But if it does not...you'll be glad you prepared.