Untar and cat time
It is very common in the Linux world to distribute some very large number of quite small files using a compressed, one-file archive created by using the tar and bzip/gzip utilities. For examples, Linux kernel (downloadable from kernel.org) are distributed in this specific manner.
So, an interesting benchmark would be to record the time needed to untar (extract) the Linux kernel .tar.bz2 file, and then to read-back the just-extracted files:
EXT4 is faster in the extraction process, especially considering the very low final sync time.
When considering cat (read) time, however, XFS is the best.
So, these first results show us that there is not a single, best-of-all filesystem. It all depend on the I/O request (read or write) and the workload type (sequential, random, cache, synchronous, etc).