While I can't say I've ever changed my carry piece based on the perceived threat.
Oh wait I can, I normally carry one 14rd spare mag, and I swapped to two 16rd when I was going to repossess a car one evening. Also swapped the 14rd in the gun for a 16rd. But that's an extreme case where I knew there was higher risks.
I do change my carry around based on weather, clothing, and even my mood.
My two carry pieces are a CZ PCR and a Taurus 38 snub. While I carry the PCR most, somedays I just feel like carrying the revolver.
I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.