Reviews are usually the easiest place to find them.
The important thing to remember: benchmarks are only a rough guide to how well a device will perform, and won't tell the whole story.
For example: the Galaxy S7 is supposed to be a gaming beast on paper, but in practice it's not as smooth as, say, an iPhone 6s (which is helped by its lower display resolution) or the HTC 10. The screen, software optimizations and other factors can affect real-world performance in a way that benchmarks won't show. That and multiple manufacturers (most notably Samsung) have been known to 'cheat' by detecting benchmark apps and running the processor at levels that aren't sustainable anywhere else.