Having taken a lock picking course, I can say that one lock is approximately the same security as two - even after 15 minutes of instruction, with the right tools I could unlock most any standard house lock in moments.
Home door locks are a deterrent more than anything else, so I'd opt for convenience.
This is not true everywhere. For example here in Sweden the second lock is usually a lever tumbler lock or some variant thereof. Way harder to pick than pin tumbler locks. What matters is the type of lock, not the number of locks.
Home door locks are a deterrent more than anything else, so I'd opt for convenience.