I consider myself somewhere in the middle, I suppose.
I usually play more casually with items on whatever stage with whoever -- I of course have my favorites but am adequate with most everyone in the game. To me, skill is more about being well-rounded, being able to adapt to any situation with any character, etc. There have been plenty of times when luck would've made me "lose," but skill persevered anyway.
I totally love playing a highly competitive match to get my skills flowing, but I can only do that for a while before I feel like the spirit of fun is lost. I prefer to improve my overall skills by playing in a wide variety of circumstances. The people I play with are mostly casual but good enough to help me improve, but I play Smash more to enjoy myself with friends than simply to get better.
So I'm a person who plays "casually," but still can play seriously, as well. I try to be a well-rounded Smasher. I find pleasure in beating self-proclaimed Tourney players at their game, especially when I can do it as Zelda with no Sheik.