I am not sure if this is the right place to ask my question. I really appreciate your help because I am really a beginner in bio statistics.

I want to develop a logistic model in a population. The outcome is yes/no and I have 12 predictors. I have no problem in the process of developing the model but the point is that I can divide my population into 2 different sub-population based on one of the predictors. these 2 sub-populations share all the same characteristics (predictors). I mean these 2 populations have been tested for the same variables but they have different exposures (exposed or non-exposed). my question is that how I can decide whether or not to develop one model in overall population or different models in the subsets??? Do I really need to develop separate models??? How can I descriptively infer that from the distribution of the predictors in overall population or in the sub-population?

Thank you a lot!