<<--Method-->>

1 (suffix _original): Original generation with no processing or upscaling. Prompt & settings can be found by dragging into 'PNG Info'.

2 (suffix _hiresfix): Identical seed to 1), re-rendered with the "Hires. fix" option enabled.
Upscaled by 2x.
Upscaler used: R-ESRGAN 4x+ Anime6B.
Denoising strength: 0.4

3 (suffix _img2img_none): Image from 1), placed into img2img via "Send image and generation parameters to img2img tab".
Upscaled by 2x.
Upscaler (Settings > Upscaling > Upscaler for img2img): None (default)
Denoising strength: 0.4

4 (suffix _img2img_anime6b): Image from 1), placed into img2img via "Send image and generation parameters to img2img tab".
Upscaled by 2x.
Upscaler (Settings > Upscaling > Upscaler for img2img): R-ESRGAN 4x+ Anime6B.
Denoising strength: 0.4


<<--Results-->>

|		| _original	| _hiresfix	| _img2img_none	| _img2img_anime6b
|-------------------------------------------------------------------------------|
| Time (1)	| 78s		| 459s		| 78s + 198s	| 78s + 202s	|
| Memory (1)	| A: 5.58 GB	| A: 8.19 GB	| A: 8.17 GB	| A: 8.14 GB	|
| Time (2)	| 78s		| 501s		| 78s + 224s	| 78s + 218s	|
| Memory (2)	| A: 5.63 GB	| A: 8.18 GB	| A: 8.16 GB	| A: 8.15 GB	|
| Time (3)	| 80s		| 527s		| 80s + 200s	| 80s + 215s	|
| Memory (3)	| A: 5.42 GB	| A: 8.19 GB	| A: 8.15 GB	| A: 8.15 GB	|


<<--Notes & findings-->>

The render time of "img2img" results is given as (time to render original image) + (time to render img2img output).

Negligible difference between all 3 upscaling methods in terms of memory usage, but Hires Fix option takes almost twice as long as either img2img option.

If you make a large batch and select a few to upscale, this also means that _hiresfix is more labour-intensive since you need to note down the seeds that gave good results, and re-render them with Hires Fix enabled.

R-ESRGAN 4x+ Anime6B has increased colour saturation, increased contrast, and less digital noise in smooth areas compared to "none" (e.g. Sunset1, dem thighs o_o)

Subjectively, I think R-ESRGAN 4x+ Anime6B renders eyes a bit better, and while all 4 options can be caught out by occasional strange anatomy, hands etc, Anime6B seems slightly worse. I suspect a lower denoising strength would prevent this.

_hiresfix and _img2img_anime6b do have some subtle differences, even though they're using the same upscaler and same settings (to the best of my knowledge). I can't pick one out as 'the best', but the increased render times of _hiresfix need to be taken into account.