QSV is performing worse than x264. What could be the issues?

[Photonive]

When I play a game (specifically Roblox) I used QSV encoder and the result was low file sized video even though it's like 5 minutes or longer when i played it, it looks like I'm recording it with a very low end pc, even though i have a decent pc (Optiplex 7050). However, using x264 encoder did better, despite the fact that QSV beat x264. So what maybe causing this issues?

Comparison
QSV: https://www.youtube.com/watch?v=kGXYjN7qzBs (7.61 MB)
x264: https://youtu.be/mBFnIXvmgKg (18.8 MB)

 

[qhobbes]

Make sure the quality/target usage is set to Quality, the Profile high, latency normal of QSV and

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Also more than likely, you're not using the same settings and different encoders behave differently when using CPQ/CRF (whatever it is). The only way to get 2 files with different encoders to be about the same size is CBR (264 CBR is more Constrained than Constant).