Best bang for the buck building combats - unique monsters and mechanics or unique/interactive environments?
In an ideal world I'd bet most DMs would love to be able to create combats with unique monsters with interesting abilities (from books like Forge of Foes) AND environments/fight locations that the players and monsters can interact with that can affect the fight. Unfortunately I don't always have that kind of time.
In your experience, if you had to choose one of those things which one helps make the combat more fun and interesting?