Which idiom should I use to convey the same as 'to put on airs': show-off or stuck-up?

Well, I think stuck up fits more specifically - in that it suggest an attitude of snobbery, it infers a social class distinction (mine’s higher than yours!), and describes an assertion of ‘caste’ superiority

But in a generalized sense, putting on airs could be characterized as a type of showing off (attention-seeking behaviour type)  - but showing off is just a very broad field of behaviours

So I’d select show-off as a clear preference

Thanks