I used to tow with a 97 Ram 1500 SWB standard cab 4 X 4. I had at the time a 16 foot open deck trailer. Only had one instance of "instability" while towing, and that was my fault as i did not have the equalizer bars setup properly. A quick adjustment, and it was fine. If you are going to be pulling an open trailer, and you use common sense while towing with a set of equalizers and a sway control, you can get by with the shortbed. If you are buying new, I'd spring for the extra $$ for an extended cab, with the longer wheelbase. I now have a 2000 CTD 2500, as I'm pulling a 22 foot enclosed Haulmark.
As for trailers, I'd never go back to an open deck. And if you buy enclosed, get the jump door on the drivers siide so you can drive a car into the trailer, then open the door instead of having to climb out the window. I also had a winch plate installed, then installed a remote control winch myself.