Phoronix published a review on the Debian 6.0 Through Debian 9.0 Benchmarks
A quote from the article:
Continuing in our benchmarks of Debian 9, here is a comparison when re-testing 6.0.10 "Squeeze", Debian 7.11 "Wheezy", Debian 8.8 "Jessie", and the newly-released Debian 9.0 "Stretch".Debian 6.0 Through Debian 9.0 Benchmarks @ Phoronix