Question / Help X264 or nvenc?

[Xaymar]

Your x264 shows threads=24 in Mediainfo, this can affect the quality with VBV/CBR. My CPU (i7-2600) makes x264 default to threads=12.

x264 is ABR, as it seems that x264 only has minimal understanding of CBR and actively falls below it whenever necessary - 6000kbit also falls below the target bitrate. It is a stable behaviour even on a single-core VM, and a higher number of threads do not affect encoding quality (disabling threading would however).

Edit: Queued additional runs with -minrate and -maxrate forced, OBS does not do this. This is "close enough" to actual CBR.
Edit: Results will be available once the entirety of the encoding has run through, will update then.

 

[Xaymar]

As promised, updated results are in:
https://docs.google.com/spreadsheets/d/1lkmYF2lphAxkdVWVy2qxgLR--88fDBTjbu4JsMF9UsI

NVENC is still only slightly worse than x264, even with B-Frames enabled for both. In some bitrates Low Latency performs better and in other bitrates High Quality performs better. NVENC handles transparency better now with B-Frames active, but it still has issues with bright flashes that happen to be near lots of particles.

From these results, I'd say that NVENC encoding is on par with x264 veryfast, but could do better in the future. You still gain small extra quality with x264 veryfast, but as NVENC is a pretty much free x264 veryfast, why not use it? It's not like you're degrading your stream as far as AMD AMF would.

Edit: NVENC Video vs x264 veryfast Video.