From my experience, I think you'd get more control with a flex torque wrench in most situations. Of course, if you are a professional, you should prepared for any potential combination that you may come across.
I try not to use universals with a torque wrench. I'm paranoid about torque accuracy but, that's me. There are times when you have to however, I try to use a swivel socket and extension in those situations keeping torque wrench straight.
Maybe its my own distorted opinion but I believe that if you are using anything on the end of a torque wrench that it will affect your actual torque, including an extension. so if you have to use a swivel then you are guessing!