I don't know man, third person is weird because it doesn't accomplish anything more than first person in a sex scene, but it does add a weird distance to something that should be very intimate. I can understand it if you want to write about all the involved parties thoughts/feelings, but that's accomplishable through being more descriptive of the job first person participants reactions.
Than again, I like first person in general so I'm probably biased.
Ditto
SPS4 explained it well + also liking 1POV
When reading pixiv (novel r18 section)
I saw a few nsfw oneshots, between 2 girls (yuri or nsfw)
and when its 3RDPOV, it feels SO DISTANT for some reason. Like : X does this to Y. Y then X.
Meanwhile, you got some nsfw ones (cough Miorine x Suletta) where it goes : "Can i really do this ?" (I feel like i shouldnt...) (Seeing her skin i ......)
ITS SO SENSUAL !
Meanwhile in chinese ero novels (po18)
sadly its also rare, but when you got stories in 1pov, they feel very "immersive", even for sfw parts.
But even the 3rdpov stories, THEY FEEL IMMERSIVE because like the 1pov ones, they feel like eroges, where you imagine yourself as one or the other party.
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Conclusion :
FirstPOV give a buff of immersion (which is basically the ultimate goal of writing/2d) but in the end, is just a BUFF/BONUS so
if the author is better at 3rdPOV then its recommended to choose 3rdPOV. (Recommended to play lot of eroges for "better writing")