I am, like most folks, some combination of the two.
Interestingly enough, for a good long time I was completely a pantser in my writing (no outline, just sit down and start writing with an idea (or an inkling of an idea)) while in my life I was a planner. The sort who memorized school schedules and maps and directions because otherwise my brain would freeze up on the spot.
This opposite behavior made some sense though, given in writing, it doesn’t matter how many times you get a sentence wrong, you can always go back and change it until it’s perfect. Could craft witty character interactions with hours or even days in between their responses to one another. You’re like a god or goddess meddling in people’s affairs. Powerful!
In real life there are no do-overs. It’s one and done. You say words backwards, you can’t suddenly unfuck them. You head for ten minutes in the wrong direction, you’re going to inevitably be late for everything, and if you sit in the wrong class or pull up to the wrong building you’ll get the immense pleasure of feeling like a moron when someone points out that you don’t belong.
Spontaneous behavior in life is freeing though. It breathes a sort of carefree happiness into your actions and there’s a lot to be said for its ability to alter your mental state. In a positive direction.
And outlining before you write can unfuck problems long before you fucked them up in the first place. (I guess that’s the purpose of planning, isn’t it?)
Which is all a convoluted way of saying that while I’m still a planner, I’m learning to be more spontaneous (though I do have to recuperate after each time), and while I’m still a pantser, outlines before you start are actually quite handy (even if I throw half of it out partway though).