Pornhwa is colored, has story arcs, has more dedicated translators and art on average is better. Hentai has a lot of weird shit like futanari, bestiality, scat, loli, shota, etc.

I will say though that vanilla hentai is miles better than vanilla pornhwa. Secret class being considered vanilla is all you need to know about pornhwa lol.

Even for the less wholesome genres like cheating, tragedy, etc. hentai does better. It gets its point across in a single chapter without having to slog through tens of chapters as you slowly contemplate on wanting to strangle the characters with each new chapter and with each dumb decision they make the way pornhwa does.