Even before fixed prices, taxi was always the way to go from Orly. I remember 25 years ago taking a taxi from Orly to a left bank address with my husband and daughter and paying less on the meter than a couple we were meeting in Paris paid, using public transportation and then having to walk the last half mile to the hotel with their luggage. they also had to use a combination of bus and metro -- now it would be Orlyval, RER and metro and then walk. We pay on average about 5 Euros more with the fixed prices for both Orly and CDG now except when we have a particularly long ride. We do pay less when we are staying in the 13th at a friend's apartment and coming from CDG. But the fixed price means you don't have to worry about traffic or a long ride.
Note also that when you use Paris public transport (which is just wonderful and efficient) that you must be pickpocket proof. No wallets in pockets, backpacks or purses carried carelessly behind you. It isn't hard to be secure but this is organized crime in European cities with very skilled practitioners and we know people who had had 20K on their cards within an hour or two or having them picked. Museum lines, cafe lines in museums, crowds anywhere, and the metro are particularly good places to have things go missing. Women use a cross body purse or inside hidden pockets in clothing in cooler weather and men can use those wallets that hang around the neck and go underneath the shirt if they don't carry a bag. If a backpack, only a deeply buried hidden pocket -- never an outside pocket or top of the bag.
