I am a relatively new Dungeon Master. I alternate DMing with a group of players; most who have been playing D&D since its inception.
I used to play in my youth, about 15 years ago; before those friends got too snooty to play, or moved away. But we always played with very loose rules, with an emphasis on story. This new group plays with somewhat rigid rules with an emphasis on combat.
My preferred play style is more of an equal mix. When DMing, I always come up with my own story, own maps, own creatures, etc. World-creating is a fun distraction and while my players don't always seem to appreciate the time I put into the story and background of the campaign, it's still fun to think up.