They are both the same. It would be better to use the past progressive/continuous tense if you wanted to emphasize the time period you both were doing something. For example, "From 8 to 10 last night, I was watching the cricket match while my wife was talking on the phone." Or, if the police asked you what you were doing last night at 11:00 p.m., you could say, "I was sleeping and my wife was reading a book."