I do want to add just in case it's not clear: both methods are equally viable in professionnal practice and usually professionnal writers are a solid mix of both, even though they'll tend to lean towards one or the other.
It can also be useful to think of outliners as being "front loaded" where most of the work comes before the first draft is written, while pantsers are "back loaded" where most of the work comes after the first draft is written. Pantsers will tend to have more extensive structural edits in draft 2 while someone who is a good outliner will be able to concentrate more on tightening scenes and moving more minor things around without completely changing which act scenes happen in for example.
Also both have their advantages and flaws. For one, pantsers tend to actually be able to finish first drafts even if they don't want to go through the editing process afterwards, they still have a book, whereas outliners who abandon a project might just have 2 chapters and 50 pages of notes. Outliners might have an easier time working in collaboration because they can make plans and follow them while pantsers might have a harder time adapting to the lessened freedom that comes with working on a team.
Saying or arguing one or the other is "better" or "more professional" is a frivolous endeavour that does no one any good.