Note that YDK provides much more than language bindings. It provides very comprehensive data validation (e.g. type, value, semmantics, etc) w/o the need to write a single line of code. Also, YDK provides services and providers that allow you to do interesting things with your data (e.g. configure a device using NETCONF or gNMI).
What pyang python bindings are you referring to? I'd have to take a look at those to be able to comment further. Thanks.