Does hardware encoding have similar quality and efficiency (quality/file size) as software encoding?

[Atom2004]

For example: x265 vs x265(nvenc) or x265 10bit vs x265 10bit (nvenc)

Maybe we shouldn't compare encoding time for now.
I'm using Xeon 2191B with x265 SLOWER preset and 1080ti with x265 SLOWEST preset. The 1080ti encoding still much quicker than CPU.

So let's put encoding time aside and talk about the quality and efficiency (quality/file size) .

[bradleysepos]

You may be interested in this HandBrake Documentation article: https://handbrake.fr/docs/en/latest/technical/performance.html

[Atom2004]

Yes, I read it. It never mention about speed up by AVX-512 instruction set.

[writersblock73]

In general terms, hardware encoders don't at this point have the incredibly intricate tweakability of software encoders, therefore tend to require larger file sizes in order to obtain similar results. Just how much bigger, in my experience, depends upon which hardware encoder you're using. As a personal example, my previous graphics card was a GTX1660. Currently I use an Intel Arc 750 which produces H265 files that are roughly 10%-15% smaller than the VMAF-score equivalent NVIDIA product. Different manufacturers have their own spin, their own secret sauce--and their products improve as time marches on. It's hard to group them together under one umbrella because of this.

But in direct answer to your question, in the vast majority of cases a software encoder will still yield smaller file sizes at the expense of taking much more time per project. As to which way you want to go, it all depends on your usage and expectations; only you can decide if that tradeoff is worth it. In some cases, you're agonizing over a gigabyte here or a few megabytes there--probably nothing you're really going to think about when enjoying the fruits of your labor. Then again, maybe you will!

Myself, my Arc shrinks things down enough that I can continue to supply my Plex media server with more material (while also not spending time on Newegg looking for hard drive deals), and the quality is terrific for the file sizes I'm getting.

The time spent encoding, for me, was absolutely a factor. I have over 500 movies in my collection. There's also multiple television series. To encode all of that with software would darned near require immortality--even if I were to spend a fortune on hyper-beefy CPUs and power bills. So for me, my "good enough" is to rely on hardware encoders. I have yet to regret that decision.