First of all i want everyone to read those

http://www.mysqlperformanceblog.com/2006/08/09/cache-performance-comparison/

http://jpipes.com/index.php?/archives/100-Benchmarking-CacheEngine-vs.-the-MySQL-Query-Cache.html

http://74.125.67.132/translate_c?hl=tr&sl=tr&tl=en&u=http://www.kodaman.org/yazi/cache-proxy-web-ustunde-yuksek&prev=hp&usg=ALkJrhhXLoRYwjz7cSXuNspw2PxQj3BYcw
last one is translated by google translate

File Cache :

If your data is not updated much and your site has static data as majority this cache system is for you.
Pros:
- Better Performance
- Good for pages which dont get edited for long time
Cons:
- Slower when updating the data
- not suitable for multi-server sites

MySQL Cache:

Pros:
- Faster
- Good for pages updating much
Cons:
- not good for mass user communities
- unnecessary server load for old pages

Me and trustmaster have Discused the future caching system, we will likely have 3 methods, and Improved more event driven cache also, a Typical SQL Cache, an optional SuperCache, along with Optional FileCache. And the admin can pick the type of cache they want

Don't forget about memory cache.

It might be in 010 but the file caching isnt implemented/tested yet (while mysql caching is working on pages and not of forums). So still quite a long way to go.