The RYA name is certainly recognisable and an obvious choice for you if you are British.
It depends what you want to do.
If you have little or no experience and want to have some basic knowledge for sailing with other people on their boats RYA competent crew is a good place to start.
If you want to be able to charter
a yacht, In Uk or many other places you will need a higher course.
RYA Day Skipper
Plus some kind of navigation