Remember, there are no render process in KK and HS. It's just a pose and capture process. Just like the games made with The Sims.
I understand why some people (me included) aren't into KK and HS. KK is "too anime" for my taste, and I never was into Hentai. And HS is... uncanny for me. I think it's the eyes.
People will also be more lenient about the image flaws in those engines. If a Daz game has an animation where the guy's hand clips through the girls leg, making his fingers disappear, everyone will notice it and complain about it. On HS and KK people accept the "engine limitations" (even if those don't exist, as high-quality games in those engines have shown) and would accept it as "normal". Same with boobs clipping in the guy's body.
There are great games in both engines (some of them going through a hell of postwork to make them look good), though.
The biggest scene I did was the foursome with Emma, Erika, and Daphne. The major issue was to find the correct positions in the "small" bed for everyone and not have them as mere audience (except for the anal part with Emma).
Rendering that scene was no problem at all. Posing it was.