PPAPI itself is a Chrome only api at the moment. I'm really concerned about using a plugin api defined by its C/C++ behavior as some kind of standard. So we not

PPAPI itself is a Chrome only api at the moment. I'm really concerned about using a plugin api defined by its C/C++ behavior as some kind of standard. So we not only have the DOM apis but also another class of APIs that have their own quirks. I'm not sure there is a great chance that other browser vendors will adopt LLVM, especially Microsoft. It will basically require them to not only reimplement the native compiler but also the frontend that compiles to LLVM bytecode and any additional SDK tools like a debugger. Asm.js is a lot easier to implement on every level. It will be served compressed so there wont be a lot of size overhead compared to a bytecode format. If you just use asm.js to call into webGL or audio apis there shouldn't be any big performance difference over using something lower level like PNaCL. Additionally, different browsers may use different optimizations when compiling LLVM code, differing implementations will give different performance characteristics. PNacl is no different than asm.js in requiring that the compiler be optimized.