Well, the two organisations are very different. Caveat, here, that I'm a BAFF member and have only read the CAFF(UK) website, so you should probably look into them yourselves. As far as I can tell from their website their primary focus is the nagging sore of the pre-75 military pension provision, under which if you served less than 22 years, you get nada.
BAFF - see the website below - is a much less single-issue organisation and is focused on the serving soldier, sailor, airman and officer and doing what it can to get them a fair go.
It's early days and a long slog, but those of us who are members are members out of conviction and we'd be delighted if you or anyone else were to join and be long with us to push these issues along.
We've achieved some media and political breakthrough and plan to continue to back up our comrades in the public domain, in which they have problems making their voices heard. We have serving and retired members in pretty much every rank.