A stretcher will not provide the spinal motion restriction like a backboard will. A stretcher is good for sleeping on, and transporting people who have breaks and fractures, a back board is good for everything.
For a backboard to function properly though, you also need the required straps, headblocks, and padding. I might be tempted to carry one strapped to the underside of my 1/2T canopy on long isolated trips, but other than that I don't think it would be of much use. Stokes baskets can work way better, and they even make carrying a bunch of gear easier with a couple guys.
'97 Ranger currently getting a HP D44 Solid Axle, lockers, and 35" MTZ's
Planning on building a custom off-road trailer...after the truck is done...