Brown is certainly a lot more versatile (or at least willing to be versatile) than Moss, IMO.
Brown is better around the LOS, on screens, better in the open field, and certainly quicker. His punt return ability adds a lot of value, too.
Prime Moss was exceptionally good at what he did -- straight line speed, stretching the field, high-pointing the ball, and working intermediate sideline fades, and few (if any) players are better than prime Moss at those things. However prime Brown offers a lot more versatility and I would argue is a better overall fit for this offense.
Brown reminds of a superior version of Deion Branch with a sprinkle of Edelman mixed in. Just see so many similarities in Brown's/Branch's respective play-styles, body control, build, etc, but Brown is a better overall player, more explosive, better speed, playmaking ability, and so forth.