Thinking of building an AR in 9mm because I dont have a pistol cal AR and most of the pistols I shoot are in 9mm. Also, this would simplify ammo logistics when going to the range.

Any preference of which system to build, Colt or Oly?

From what I have been reading on the diffrent boards, the Colt system is more finicky and takes more tuning than the Oly system. Anyone have experience on both these systems?