Ah, kids these days... won't read anything longer than jingle.
It's not about what I consider better, it's about what the guy who posted claim considers better. And he literally said Vulkan "offers better fps, visuals and dev friendly".
But hey, let's ignore actual contents and post whatever we like, right?
NB I agree with all that you said and I'll take a cross platform API any day, but that was never the issue here.
I think you missed my point. Even if you can consider the two equal in performance, everything else would indicate, (at least to me,) that Vulkan would be a better API given its reach. I'm giving DX12 the benefit of the doubt on that one but, all of the benchmarks I've seen haven't shown anything amazing going from DX11 to DX12 but, going from OpenGL to Vulkan seems to have more occurrences where performance improves by more than just a couple FPS. Also, you keep using the term "better" which doesn't really just mean performance. If you're going to talk strictly performance, don't just say "better", because that's far to generalized of a statement to derive just performance from such a statement.
None of the games supporting two or more APIs is a true benchmark of the APIs, since "all" of them use some kind of abstraction/translation layer. E.g. Valve games and Croteam games makes all APIs behave like Direct3D 11, so any gains will be due to generic optimizations rather than the API itself.
Ehh, that's only because Valve wrote a translation layer on top of the already existing use of D3D APIs. You can get the same kind of benefit in OpenGL and DX11 by doing some simple thing (that nVidia cards actually probably do under the hood,) and that's accepting the draw calls and just putting them on a queue (just like command buffers,) and executing it later when there is time or when a command is run that needs to flush the queue. This is actually the primary reason why games like Doom really see no benefit using Vulkan with nVidia cards. There is enough black-boxed optimization that is essentially doing the same thing.
One of the reasons why you see some OpenGL games get bigger gains is not the API itself either. If the games were written in OpenGL 4.5 with AZDO API calls there would be nearly no gains at all, but most OpenGL games are using features older than OpenGL 4.3, some even still OpenGL 3.x. That is after all the advantage and disadvantage of OpenGL; you get to choose between old and new features, which often leads to new games still using outdated API features. Even though I've experienced these new features in action, I've never seen them used in games.
That's not how OpenGL works. Every revision tends to add new features the OpenGL as a whole, not move already existing functionality. This is super important for backwards compatibility. If you're using version 4.3, you can basically use everything from 4.3 and earlier because 4.3 isn't going to have simple things like, making a draw call, you need to use OpenGL 1.x for that but, that doesn't change that your maximum supported version is 4.3.
At the moment Vulkan has one disadvantage over OpenGL; no support from Apple. I hope this will lead to developers abandoning their crappy platforms, and that Apple will live to regret their decision. But my greatest concern is whether Vulkan will get enough foothold on the desktop. As we know, OpenGL development has primarily been driven by the needs of professional graphics, which happens to align well with the needs of desktop gaming. If Vulkan ends up being an Android-"only" API, I'm afraid the direction will focus on embedded low-end devices, and Vulkan being dead on the desktop.
Definitely a valid concern. Apple doesn't really care because they have Metal however, that's not a huge concern to me because, Khronos made is clear that Vulkan was not intended to replace OpenGL. Vulkan was intended to be another option for applications that required high efficency and better low-level control at the expense of complexity and greater control of just about everything. OpenGL is still expected to be used in cases where the workload is light enough where using Vulkan for optimizations wouldn't yield much benefit but, would still take added time away from dev. Simply put, the right tool for the right job and Vulkan isn't always the right tool. I don't think that it will become a mobile-only API for that reason. Mobile devs would prefer OpenGL if it's going to fit the bill because, it's easier to use.