咱(zán)们(men) involves the speaker and listener while when using 我(wǒ)们(men), speaker sometimes do not get the other side of the conversation. For example,
Nǐmen qù nǎlǐ
You go where
‘Where are you going?’
Women qù kàn diànyǐng， nǐne？
We go to watch movie and you
‘We are going to watch movie, and you?’
From the example, we can see that the other side of the conversation is not get involved into ‘we’.