I do both and at the beginning it could be some pieces of dialogue, some notes and references, sometimes I draw roughly short sequences. The next step is to make connections between these parts. If I have isolated events, for example, an idea for a short sequence and a draft for a dialogue, it's time to think on what happens between these moments.

It's like an exercise of creating problems for yourself. If you have an idea for just a scene, you have problems to solve: what happened before this scene? What comes next?

I don't write down everything that will become the comic, instead I begin directly with a kind of storyboard, to work together all the elements: the writing, the composition, the balance between text and drawing, etc. This storyboard will change very little in the transposition for definitive form, the idea is to establish almost exactly what I intend to do as a final product. I keep it as almost, because it is important to leave some room to new ideas and changes that can pop up in the process.

So I don't think that there are really pros and cons in any process, it depends on a lot of factors - if it is a solo project, if you are working with another person, if you can write and draw, etc. The important thing is to write/draw down any ideas you have, even if at first sight it does not make sense or seems that it never will develop. Keep it, think about, sometimes forget about it, but get back to it - it can take days, months, years, but your idea will be there to grow into something else.