What is thee difference between Bing Speech API and UWP Speech API

I found two interesting alternatives in order to give to my desktop application the capability to understand some command.

1. Bing Speech API, that is a rest interface to convert speech to text (in order to put the translated text into a search form, for example)
2. UWP Speech API .

But it is not clear the difference in terms of:

A) costs. Cognitive website explains several pricing plans. UWP is free instead? B) customization: CRIS service, within Cognitive, is customizable. UWP is also customizable? how Can i customize the dictionary?

Let's Do what Mother Microsft sometimes doesn't make : clarity

Thanks a lot guys! ZAR