I hope this doesn't seem like a cop-out answer, but I find that it honestly depends on the project. I myself tend to default to storyboarding (both long and short form), but there have been projects that I scripted, just because that made more sense / felt right for that work, and one long-form comic somehow came into being as an oral recitation that I held in my memory and edited by repeating it back to myself. That was a weird one. Most comics don't get created by verbalization, and I wouldn't recommend it. But hey, that was the baby left by that particular stork.
I would go with whatever allows you to create your work most efficiently. If you're a storyboarder, develop your storyboards. If scripting comes naturally, work with that. And don't forget, you can combo up techniques - write a script, with storyboarded sections where, say, staging is important, or there's a lot of action. Or rely mostly on storyboards, but take written notes on the side to keep larger lore details straight. I'm a big believer in the Church of Whatever Works.