i have flown the atr and now currently fly the 737. the 737 is better since it is jet and you can climb out of the wx. i know that there is a big demand for atr captians all over and most of them pay the same as a 737 position. the atr is small and light so there isn't as much momentum controll as the 737. with the atr you should be able to kepp it a t 250 until 4 miles out and easily make the required speeds by 500 ft. anything less is lame and you do not know how to fly a turboprop. that is the only main advantage. as far as fun to fly. the 737 is much better. the atr is lame because they procedure to death a very easy plane to fly. my grandma can fly it. it is very hard to mess up and get behind the plane thus requiring no skill just an ability to memorize procedures. the 737 also hand flys better. for some reason the atr seems to be bulit to use the auto pilot.
I would agree to get 500 hrs in the 737 first then move on. the atr is fine but it gets old very fast for someone who has some skill and would like to show it.