Unweighted Stats: represent everything used on Showdown equally. A player at 1000 and one at 1700 have the exact same influence on these statistics (so you'll probably see a few trashmons).
1500 Stats: represent what the average player sees on Showdown. While these stats are more significant than unweighted stats, they tend to feature only minor shifts from unweighted stats.
1630 Stats: represent "standard" stats, what the typical competitive player should see and be prepared for. These stats tend to be much more significant and revealing than 1500 stats.
1760 Stats: represent what the best-of-the-best in the metagame are doing. To some extent, this is what all players should strive to be doing, but there are some Pokemon and strategies that are difficult to pull off and might require a greater amount of skill than the typical competitive player possesses.