i think freecities is the best for large-scale domination/humiliation stuff, course of temptation is the best for yume (even though i played as ike, it was just too slow to think of it as anything but a dating game with porn), and degrees of lewdity is best for corruption of a single oshi
the erotic prose really isn't that great in freecities, but it's fun to fuck around in. it's also *really* customizable with how you can easily swap organs around (i accidentally left my zeal too long in the dairy, and he turned up being immobilized by a hyperdick and balls, so i grew a new dick and balls for him and he was right as rain in a week/5 minutes irl)
you can accidentally turn your slaves into tgirls really easy which is annoying as hell, but it's just a label so it doesn't change anything
i haven't gotten to the part where you can gene edit slaves into different races, if it exists, so i could have a japanese shu and british mysta (shu requested me to buy his twin so i made him mysta) while them both still being labeled as brothers. i can't figure out how to clone someone and implant them as twins either
the erotic prose in course of temptation is fine, i don't think i've ever gotten off to it, but it's fun as a yume dating sim. you can't have a monogender world which is annoying, and sometimes it takes awhile to be able to rename someone.
i think i had hakka as my best friend and sonny as my roommate but i never got far enough for uki/the roommate's boyfriend to consistently target ike/me which seemed like the most fun
i think the sex mechanic granularity in degrees of lewdity is perfect and makes for some awesome sex scenes, even if it gets repetitive. you can't rename the characters so it isn't fit for making a nijisanji world, but it's fun for getting off to really degenerate shit
less customizable than freecities, and it doesn't play too well in being anything but a submissive even when modded imo. fixing corruptive affects is annoying and expensive unlike freecities, and the PC has a low pain tolerance so you can't just let a train run on him or the scene will end prematurely with him injured