I was really impressed by Polly in the novel for The Highlanders, there she was certainly the equal of Barbara in guts and smarts.
The Highlanders is definitely the high point for Polly - she runs rings around the English soldier Lt Ffinch and keeps telling Kirsty to stop crying and (wo)man up. The problem is the writers were inconsistent about stuff like that and there are stories where Polly is a bit pathetic - exactly what she tells Kirsty off about.
Vicki was also a huge step up from Susan and didn't really have the crying moments - she happily tries to poison Nero in The Romans and leads the revolution and saves them all in The Space Museum.
Victoria has less of those moments and Dodo doesn't really get any decent material - though she is the one that figures out something is wrong in The Savages.
Zoe is generally well handled as they usually always remember how smart she with only the Dominators being a bad story for her.