Difficult I like both my first VN game was Acting Lesson. And here was an interesting story and nice action. Btw I found the interaction in other games very nice. Lian from Acting Lesson is the brother of Martin from DMD.
I like gradual progression, especially if it's a incest game. Keep me teased/aroused, and I have no problem if it takes a while getting there. What I dislike are fillers, i.e. dream sequences and similars
So I don't mind a decent story, but I'm going to skip through almost all the story on my first playthrough either way... That said I prefer to skip through less so I guess fast is my preference.
Usually want the first actual sex scene to be fairly early on in the story, but then I like them to be spaced out a good amount. Take too long to get to that first one and I start thinking you're stringing me along. Pack the rest of the sex in too tightly after that and I yearn for a break from the constant coupling. There's a balance in there that you've gotta strike for me to really enjoy it.
Writing quality determines that for me. I'd rather just have the saucy scenarios with a tiny amount of background detail, than go through an entire story that leads to that saucy scenarios if your writing is shit.
Unfortunately the ability to both construct an appealing lewd scene and your ability to write them sometimes go hand in hand.
I have no problem in playing in either, but I find it that slow burn games needs to be of high quality in order for me maintain my interest in it. Whereas fast burn games, I can just get go through it quickly and be done with it even if it is not so great
Slow burn can be absolutely great but also stubid and boring. For me it has a higher ceiling and a lower floor in terms of quality writing. "Fast burn" is often more fun (lower risk of dissapointment).
With good pacing it can be rewarding too, but imo never as good as an excellent slow burn game.
Slow burn, but I've seen good games getting milked by the devs who refuse to provide any good ending.
Imagine waiting a year to get an update for a game which has 20 mins max worth of content and then seeing the dev whining on Patreon about how they're losing money...