I've decided to add some concrete examples from my session last night to make sure my stance on the matter is clear:
Encounter A: the PCs (a necromancer and an assassin) surprise 4 cult fanatics sitting around a table eating a meal in their shared room. No need for minis because the environment is simple, the positioning isn't going to matter beyond is/isn't near the table, and the fanatics might not even be getting to take actions (as evident by the way it played out: one fanatic killed on the assassin's first turn, the rest stuck in a web spell, then another fanatic dead on the assassin's second turn, and one wounded by the necromancer, then the fanatics cast some spells trying to paralyze the assassin and damage the necromancer to break concentration, and died within the next two rounds for failing to do either).
Encounter B: the necromancer, two zombies under her control, and the assassin are in the cult's temple, when they realize a giant constrictor is hiding inside a bell near the center of the room, and it slithering out sounds the bell, which is answered by 3 of the four entrance to the temple opening and enemies coming forth; the cult leader from one, 20 skeletons from another, and 20 zombies from the last - so out come the dungeon tiles to show the room and its furnishings and a detailed position for each of the 46 combatants. The great benefits were knowing how quickly each party member got surrounded, and how many of those zombies were in the area of the lightning bolt spell the assassin cast from a ring of spell storing. In the end, the battle was memorable for the players, but the necromancer player is lamenting not having chosen any area effect spells as of yet (but she is 34 experience from reaching 7th level, so I expect she'll be remedying that very soon).