I have a slider hitch with a short bed. The only time I've used the slider was to experiment maneuvering with it. (My 5er does not have the indented front panel). I try my best to not get in situations where I'd need to turn so sharp as to be concerned about making contact with the cab. Turning that tight is very hard on the 5ers tires due to the side-slide it causes. I've never wished I had a long bed.
P.S. This is indeed a good point, romor: "...a long box would have required a slider to keep the bumper from hitting the trailer in turns."