• Which download option provides the highest visual quality

Which download option has the best visual quality? The 5K/6K SLR-encoded one or the "original" to its right? Can it differ on a case by case basis?
Is the SLR-encoding making any trade-offs to achieve the sometimes significantly lower file size? Shall I download the SLR-encoded file when 90fps interpolation is available and the studio-encoded "original" otherwise?
I probably should mention that I do not care about the file size at all (apart from feeling a bit bad for using more of your server bandwidth). All that matters to me is visual quality.
Thanks!

a year later

[unknown] Nothing has changed. If all you care about is visual quality and bandwidth/file size doesn't matter, then the full-size original is still the best option.

Though usually (at least for me) the difference in visual quality between the original and the "max" 6k/5k/etc version is not a whole lot, personally I just download the original version for my absolute favorite scenes.

Keep in mind you might need a slightly more recent/powerful GPU to handle some of the full size originals due to their much higher bitrate.