All the different numbers -be it your spouses client ID, your client ID or the application file number- contain the same information. The only differerence is that the different client ID's would have either your mailing address or your spouses. For myself I have looked at them all and thats the only difference I've seen. When checking the application file number you use the sponsored person's information, ie name, DOB, country etc. Its sometimes bettter to use the sponsor client ID because when using it you get both sponsor approval status as well as visa office info such as the date they received it in POS and medicals when they get it. But again the information is all the same.