benchmarks for cache disabled/enabled and file cache vs. apc/memcache

When should you and shouldn't you enable the cache?

If using the file cache, at what point should you choose the option to divide into fragments?

Has anyone done any benchmarks of performance with
1.) cache disabled
2.) file cache enabled
3.) apc
4.) memcached

Obviously there are a ton of variables (site setup, server specs, traffic, etc.) but I'm just wondering if there are a few example benchmarks to get an idea of how caching impacts performance and at what levels one has an advantage over another.