I have not run enough supercharged vehicles to know for sure, but these are the opinions I have heard on the matter.
-Solid Couplers have a better response, and are more reliable.
-Spring loaded couplers are quieter at idle.
Both solid and spring loaded couplers were used on SC's. The late model m90s use spring loaded while the early models use solid. I have only ever seen solid aftermarket units, but I havent looked around too much.
Personally the solid unit makes me more comfortable, fewer parts to fall off in the case nose and no metal parts.