Not bad options -- each carries a warranty. I would definitely cross off Options 3. It has no advantage over Option 4. Cross off Option 2 unless you have a good feeling on who is doing the rebuild. I would go with factory over somebody else's rebuild any day.
I guess it depends on the mileage and age of the used tranny and whether you can trust what they say. Salvage operators have a habit of saying 50,000 miles for any part they sell you.
At only 70,000 miles it seems a quality repair is in order.
95 E320 Cabriolet, 131K