In general traffic I doubt you would ever need a slider with todays cut corner cap fifth wheels. Maybe when backing in a tight site but I try my best not to cut super sharp anyway because of the twisting and scrubbing it does to the fifth wheel tires. But every fifth/truck combo is different, as for me I have plenty of room.
I do however have a manual B&W slider and the only reason I have one is because I have a steep hill I have to back down to get to the barn and this provides a steeper angle without hitting the tailgate when backing down. Hope that made sense.
Had a Pullrite auto slider for about 5 years on a previous fifth wheel years ago and to be honest I didn't really care for it. I had too many times where I had to separate the head from the rest of the unit just to unhitch plus I was always cleaning and greasing the slide bars. Plus in my situation it wouldn't work for my needs.
Dan