Looking at the replies, there's actually an interesting split. I think both have their merits, so you should find the path that's right for you (which may be different depending on what you are writing and where you are at as a writer).

- fastest way to get better as a writer
- quickest way to get to grips with the character and story
- best way to grow your readership

- best way to get readers deeply invested

Ultimately you've got to find you balance - the best you can do as fast as you can do it. I'm still figuring out mine...