Realistically average would be my preference (if I had to choose one). Personally it does not really matter what size the dick is so long as the sex being had is great, but once you get over a certain size it does kind of put me off in terms of enjoying the volume/chapter that I am reading.
If it's not realistically sized...sometimes I question whether its even a penis or how it would even work (too big -> erection=death due to lack of blood in vitals, too small -> lack reproductive abilities)
Realistic to larger than for hentai/art purposes. Nothing too crazy though unless the work is created to be comical such a futa having an arm length dick or something along the lines of John K Peta's works. I like seeing a slightly bigger dick in H works to visualize the male anatomy better for fantasy purposes. Similar to how women have larger boobs in hentai, if they can do that then let there be big dicks as well lol.
Realistic to slightly larger than realistic. Agree with Misaki_chi, it's a matter of enhancing what reality looks like for visualization/fantasy purposes.
As a straight dude my preference may come off as odd but the bigger the better. I imagine bigger dicks as being able to feel more and feel more intensely for whatever reason, whether it's through intercourse, blowjobs, paizuri, whatever else. I imagine that because the penis is bigger, that intercourse is more tight/feels more intense hence it's more pleasurable. It's kind of why there's a side benefit for me to reading loli hentai, that because the girl is smaller the pussy is tighter and feels better in my mind, even if the dick is average-sized. Honestly, because it's fantasy realism has no relevance to me.
If it's vanilla, or something with a more serious tone, I like the proportions to be accurate. Any other genre, I care not about how ridiculous the proportions are. I encourage outrageous designs, to be honest.
Anywhere from realistic to slightly larger than average works for me, but I voted for realistic because... let's face it, tons of hentai out there always have the catcher comment and gush about the big size of the penis. So when it's about a normal size but the girl feels good from it, it's a nice change of pace.
normally average size works fine, however in certain circumstances its pretty hot to see a small loli taking a larger sized cock, or there was than doujin with a woman who was cursed with a horse cock and banged a bunch of her students which was nice >.>
Yup. Only in hentai will there be lolis enjoying arm-sized cocks. Realistic is good too and itty-bitty cocks could be used as a sweet vanilla plot device, but it's the XXL monstrosities that will pose a problem in other visual media so I take the opportunity to enjoy them properly in hentai =w=
Objectively I look at this the same way as I do with boobs (read the boobs poll for my answer there). Subjectively I don't think about it that much since I don't get turned on by seeing penises.
One thing I will say though is that I don't like it when they're overtly veiny and thick. I prefer it slim and smooth ;)