The other day, we were helping a long time client with setting up a new development server configured with Ubuntu Server LTS 16.04, which comes with PHP 7.x. Benchmarks of PHP 7.x show that it is faster than any PHP 5.x version by a measurable margin, hence the client's attempt to move to the newer version of Ubuntu and PHP.
But when we tried benchmarking the new server against the existing server, which has Ubuntu Server LTS 14.04, showed that the new server is extremely slow compared to the existing one.