I compared and decided for the Quad-Lock. However, there are a lot of cases where modern Smartphones get killed by the vibrations when mounted to the FTR - independent from the choice of mount you make. So I drive with a TOMTOM Rider 550 on a RAM Mount now and use the Quadlock on the bicycle.
Got the SP Connect for years on HD and Buell (even bicycles) .. IPhone SE (older one) and there are/was no probs.
Can´t say what´s better.. never used a Quadlock one.