Phoronix published a review on the Ubuntu 6.06 To Ubuntu 16.04 LTS Performance Benchmarks: 10 Years Of Linux Performance

A quote from the article:

As I'm in the process of retiring an old AMD Opteron dual-socket system, prior to decommissioning it, I figured it would be fun to go back and re-benchmark all of the Ubuntu LTS releases going all the way back to the legendary 6.06 Dapper Drake release. So here are some fresh benchmarks of this AMD Shanghai system with eight cores and 16GB of RAM when re-benchmarking the releases from Ubuntu 6.06 through the latest Ubuntu 16.04 LTS development state.

Tested for this comparison were Ubuntu 6.06 LTS, 8.04 LTS, 10.04 LTS, 12.04 LTS, 14.04 LTS, and the latest development state of 16.04 LTS as of this week. While Ubuntu 16.04 LTS isn't being officially released until April, this upcoming "Xenial Xerus" release already has GCC 5.3 and Linux 4.4 as will be present in the final build. Testing wasn't delayed until April since as mentioned I'm in the process of decommissioning this power-hungry system.

 Ubuntu 6.06 To Ubuntu 16.04 LTS Performance Benchmarks: 10 Years Of Linux Performance @ Phoronix