you may loose a SLIGHT amount of turning radius, but you shouldn't need to turn so sharp that the stabilizer bars are in a bind, and backing is no problem, possibly made a little easier, as your trailer wont be so twitchy with the bars attached. You will notice the improved ride quality, immediately.
I talked my dentist buddy ( 300K salary) into getting them for his NEW car hauler trailer. He has a 60K monster Dodge diesel, a new 4K flatbed, towing a 60K race car, but didn't want to spend $300. for the stabilizers.... WTF??... so the second time out with his race car, his wife was towing it with the 3500 4x4 suburban, he was leading with another larger trailer. I don't know how, but she lost control, hit the center divider, spun the whole rig 1 1/2 times around on a 4 lane freeway, the trailer slapped the L side of the Suburban, did lots of damage, rolled two tires off the rims, but held tight and together. The first cop on the scene told him the only reason his wife and daughter didn't roll, crash and die, was because of the stabilizers. one was bent bad, and so was the tongue of his new trailer. EVERYONE LIVED......and really no injuries, other that scared s##t less that's the best reason of all.