I would select 3 hr 20 min connection without thinking twice. What if your flight is late? What if the cruising time after landing will be longer (sometimes planes land and had to wait for either spare gate or move away and use buses to transfer passengers to the terminal - it might take 20 minutes easily)? Keep in mind boarding also closes 20 minutes sharp before scheduled flight time. I doubt the luggage will make it on time with 50 min. connection. I wouldn't risk it and get longer connection just in case.