There are different types of cache.
I have stopped using eXtreme Styles because under load testing it falls behind as far as throughput. That's a template cache.
You can also cache frequently run queries like the board_config table and the themes information. I don't know that I've seen a comprehensive MOD that does all of that thought. On my board I cache the config data, themes data, smilies data, and a whole lot more. The advantage of doing this is you run fewer queries through your database for data that doesn't change regularly.
You can also do caching at the database level. MySQL offers sql caching as well as index caching.
So the question "which cache is best" cannot really be answered without more detail.