Ok, this is a hot topic right now, so here we go. Which is more important? Both, imho!
I believe that marksmanship practice builds your confidence as well as your skills. Self defense practice; drawing, moving point shooting, shooting from different positions like standing, kneeling, etc., builds your defensive skills.
You never know what your situation might be. Being able to respond quickly may be critical but you may need to take a precise shot around a loved one.
I have written several time, Practice like your Life may depend on it. I believe that now more than ever. I practice marksmanship, I practice accuracy, and I combine the practice so I can draw, shoot rapidly without sights and then on demand take that precise shot.
If you need a precise shot and you haven't practiced, can you make it? If you need to defend yourself quickly, can you?
Practice smart, practice safe, be safe!