it's the same story with the two, with the difference that nvidia is not pretending like they are doing open standards.
This is not the good type of competition. The good kind of competition bases on the same conditions, i.e. GPU vs GPU. if both manufacturers release their own APIs that is just going to cause extra work for the devs, more bugs because they need to fix the game twice pretty much and more money out of your pocket for privileges.
It's not open standard, else nvidia cards would benefit from it as well. You can give your opponent a highly promising gadget and call him an equal, but without the manual he will never figure out how to use it. That's just marketing bullshit to make themselves look better than DX12.
Quit with the "aww that poor poor manufacturer AMD getting bullied by the people on the internet" story, if nvidia would've released mantle i would be saying the same.
What don't you understand about games being buggy because they are rushed and not because of the work involved?
It's like you don't want things to evolve and get better, Mantle is a steeping stone towards better things. Whether it means DX12 being even better or another API being even better DX12.
Mantle is what will push things forward and offer improvement in both game development and game performance.
All competition is good competition because it's what drives things forward and improves things. Without it things stay the same and never improve.
Mantle is also open standard, it was designed to run on GCN but it's not Proprietary. It's open to the developer and it's in their hands, if they want to make it work on Nvidia cards or not then that is up to them but there is nothing stopping them from doing it.
And awwww AMD getting bullied is not my sob story, its a common thing on the internet and it's sad to see. I'm so sick of people looking at things as AMD vs Nvida and thinking their chosen brand is better than the other and reading their smug comments and slurs.
Mantle is about improving game development and performance, it could be made by Tesco's for all I care. But as usually because it's AMD there are all the childish idiots that want to see it fail or don't want is to do well because of the simple fact it's AMD.
It's not about who made it, it's about what it offers, how it improves things for the industry, people who play games and creating competition which will further push things and make even greater improvements down the line.