Call me bias, but I'd argue the coding is the worst part. At least for Ren'Py. I can't draw to save my life, but I can write and I write good. Sure, I get writer's block, but I can still kick out good content when I'm free of it. But coding just suuuuuuuuuuuuuuuuuuuuuucks. I'm working on an RPG project, battle system et al, and I'm coming up with these unique enemies and allies and places (I don't want to overuse things like Orcs and Goblins, so I went with Eldrich designs and oddness). I can write sex scenes and descriptors with ease, I can write battle text, code all the triggers and flags for unique scenes, I have a randomized greeting for each character based on a dice roll for christ sake!
But if I accidentally put a W instead of a w... Then fuck me sidesaddle on a salamander's sink ship, cos my project will self-destruct and I'll spend the next month trying to figure out how the fuck it went wrong.
It's a headache to deal with and the forums are all but useless as they talk like you already know it. So coding. Definitely coding.