That really depends on the game. This year, there’s only two loading stations, only (up to) six null hatch cargo bays, and some real possibility for congestion on the sides of the cargo ship. In somesituations, you may get the same or even better offensive production out of two robots than you would get from three robots trying to share that space (let alone 4 if the opponent sends a defender). This is especially true if multiple robots on your alliance are cargo focused, as you can quickly run out of bays on the cargo ship and knocking cargo loose on the loading area tends to significantly slow many hatch loaders.
Granted, I played in plenty of 3 offensive team matches this past weekend at Westtown. There were a bunch of teams that didn’t plan on being able to retract into their frame perimeter, so they couldn’t be asked to play defense. There were other times when we were more confident about being able to share loading areas, knowing teams had specific dimensions or drivetrains that could work in corners together.