Provided good ammunition is used, at typical LE distances of 100 and in, from a terminal ballistic perspective, both a quality built SBR and 16" will provide adequate performance. Obviously at extended ranges, the 16" will be a better option. SBR's are certainly more convenient, especially getting in and out of vehicles and in tight spaces. SBR's do have more blast, flash, potentially reduced lifespan, and can be more temperamental in function--although the better quality ones run well. An SBR with a suppressor is about the same length as a 16" gun--this is a key fact. An ideal LE rifle is a quality built 11.5-12.5" AR15 run w/can; if that is not available, then a 16" gun makes a lot of sense as a general purpose rifle.