Question was closed. Allegedly it is opinion based and questions design decisions though in fact it asks for reasoning and addresses considerations for using of one or the other which violates Stackoverflow's question policies. They want the questions once a developer has made the wrong choice and runs into an issue whereby they can answer with something like "you need to the kernel termios api not the C library's. In short they don't want to inform.
Turns out termios is implemented in some kernels and there are reasons for doing so. But Stackoverflow won't be the place to find the answers as to why and hence which to use when and for what reasons. That would be too informative and educational for Stackoverflow. And beyond the knowledge of most if not all of it's mods in this case. Definitely that of it's founders.