Definitely painting, especially with big things like boats. Overspray and paint dust make so much mess. I used to build 1/43 resin car kits, and 1/35 military. Painting them was OK, once I got around to making a small spray booth with an extractor and used an airbrush rather than rattle cans.
Is it even possible to paint a boat hull with an airbrush? I imagine keeping a "wet edge" would be impossible?
Windows runs a close second. I used to use Microscale Kristal Klear for cars. easy to work with, as any excess can just be wiped off after setting with a damp cotton swab. No good for boats, as the windows would just fall out when it got wet. Canopy glue is much harder to work with