Whilst Makaton is sign assisted language, BSL is a language in its own right, meaning that it has its own structure. I don't know much BSL, but I grew up with quite a lot of makaton and I really enjoy learning that! I find that, when I do want to pick up a little BSL, it means that I'm more used to using my hands to communicate. It depends what you want to use it for, tbh. If you want to teach in a setting which mainly consists of hearing children some of which may have communication difficulties, makaton may be more helpful. If you'd want to teach in a setting which may include deaf children, BSL may be more helpful. This is what the makaton website says:
Makaton is designed to help hearing people with learning or communication difficulties. It uses signs and symbols, with speech, in spoken word order. BSL is the language of the deaf community in the UK. It is a naturally evolving language, with its own grammar, word order and has regional variations.
I don't know if anyone else does this, but I just tend to watch Justin Fletcher videos when I want to revise some makaton... there are lots of other videos which are helpful, but I also grew up with Something Special, and it works so I have no reason to change (although I do use other youtube sources occaisionally)