Depends.
In D&D, it's mostly described. I may diagram confusing or awkward battles, but really all I need to know his who is next to who, near who, or far away from who. It's a handful, but since we don't have a table, it's the only real option.
In FFZ, I've tried to remove the grid without removing most of the strategy, and so there's an Abstract Combat System for running combats without much muss or fuss. There's two ranges that define where people are in combat, and the terrain can vary tactics (though it doesn't have to). It's a lot of fun, really.