For lens collimation, I suggest DAG. He has a collimator, Youxin doesn't. I have used Youxin for a couple of my Leica IIIFs, so he is excellent with cameras. Based on your criteria, you have cost effectiveness and excellent outcomes with DAG. However, speed is not in the equation. I've waited up to 2 years to get some of my stuff back.
With Don, if you pressure him, he will get the job done but he will charge an extra premium. OTOH, if he knows that he's taken a long time with your gear, I think he actually discounts his pricing somewhat to compensate. The work also seems to be done in a less hurried, more considered fashion. The 2 year wait was when I sent him a large batch of lenses to overhaul and collimate, along with my IIIG to work over. That was when I was on a 85, 90, and 135mm lens kick.
Gus Lazzari is also a perfectionist, but he does charge more than DAG. There was a time when he closed his business to new orders, because he felt that he was getting too backed up. Gus will clean up the cosmetics too. DAG leaves that up to you.