Personally, I feel the radial pin is superior in every aspect to the 5/16-14. For one thing, it screws directly into the wood. The 5/16 joint has an insert in the shaft. It's just more complicated than the radial & I believe minutely takes away, absorbs some feel. I refer to K.I.S.S, keep it simple stupid. However, I am a firm believer than any joint is good as another so long as the shaft locks down to the butt securely. The only difference, which again is minor, would be the vibration dampening effect.
But in this case i'd bet the thing hendering you is the balance. Find the balance point on each cue & note the difference. I'd bet the 5/16-14 jointed cue is very front heavy with a standard shaft, and by adding a lightweight Predator shaft it brings the balance back to a more comfortable & familiar feel. The radial pin cue likely already has a nicely fit balance points with the standard shaft. The balance point most people find most comfortable is between 18.75" & 19.5" from bumper. That's a small 3/4" window when considering a Schon cue is 58" long.