In weddings you would shoot F1.2 in controlled scenarios anyway. shooting F1.2 in Servo is asking for trouble. I don't find too often that i need servo at weddings other than when they walk down the isles and dancing or the occasional fun group shots that have motion but then who would shoot F1.2 with groups unless you can line them up on the same plan of focus which you often don't have time to do. I just got mine so i can't comment based on experience but i have read the 85LII is very good tracking subject when in servo. On the other hand i will never recommend always being in servo mode as many people do. Fast Primes struggle taking images of static subjects in servo. You should only shoot servo if there is movement. I cannot express that enough. Ive been preaching that message for some time. If you don't believe me just do some tests shooting servo/ then single shot around the house, typically what you get is a prime going in and out back and forth if in servo. The 5dm3 has calmed this down a bit over my other cameras and no doubt the 1dx has also but lern this property about primes and you will get more consistent quality in focus shots.