don't get legal help etc with BC's bronze package
Bronze is actually aimed at race organisers but anyone joining a BC-affiliated cycle club is automatically given a 1-yr free Bronze membership in order to allow them to get a provisional racing licence and "try it out" – if they like it they buy a Silver or Gold, if they don't like it then it hasn't cost them anything.
It's not aimed at commuters – that's what the Everyday Cycling package is for.
TBH you won't go wrong with either. Join BC and you're helping to support world class athletes, grass roots cycle sport, coaching for kids etc.
CTC are a bit more advocacy based – cycling in general, the SMIDSY campaign, rights of access that sort of thing.