I decided to run some of my own tests in Dota 2 to see what kind of difference I am actually seeing, the results are surprising.
With many thanks to the person behind the recent video I covered , I was able to get a fair bit of help from him on twitter. I used the same demo file he used to run my tests. This demo file is heavier than the one used by Phoronix and others. Every demo file will give you a different result remember.
All tests run with "desktop friendly fullscreen" mode, not the borderless window mode which is a different option again.
Each test was run four times with the first removed to allow for all systems cache to be built for more accurate results. Tests done using the Dota 2 built-in benchmark tool using "timedemo benchmarkfilename", I simply ran Dota 2 with these launch options (console + API):
+con_enable 1 -vulkan
+con_enable 1 -gl
The benchmark does change graphical settings when you switch resolutions, so don't "do a Liam" and not notice. Make 100% sure the settings match after changing resolutions.
Note: As this is a benchmark, please remember this is probably different to what you will achieve. Unless you have the exact same setup your results will vary.
Linux Mint 17.3 64bit (Moving back over to Ubuntu soon, but that's another story)
Linux driver: 364.19 (latest available for Mint)
Intel i7 5960x 3.0ghz, 8 cores
So in all the Linux tests, OpenGL outperformed Vulkan in Dota 2. Not by much at all in 1080p, but 4K is a different story.
I would love to run some Windows 10 tests in comparison, but Windows wanted to update which slowed everything down, Steam kept going to a 0b/s download for Dota 2 and it's just...so slow. I will hopefully do a Windows 10 comparison when Windows actually plays nicely. I was on it for half an hour and it only got to 40% done on updates, so it would probably take all night to do that + the tests.
Finally, just to remind you that Dota 2 isn't the best benchmark for Vulkan, Valve said it themselves that Dota 2 isn't doing all that much. Vulkan is early, Vulkan in Dota 2 is also very early.