Personally, I dont see any reason for CM to kill Michael. CM had a chance of a lifetime indeed, tons of money, an exciting experience, not to mention the publicity he could have made afterwards. He would not have needed to work for MJ after the tour, considering the amount of money he would have made, some months even without working at all. And if MJ knew he could count on CM for propofol, no doubt he would have turned to him in case he needed it again in the future. That's why he wanted to be the only one caring for Mj's health : hence the comments to Kenny. He wanted to keep Michael under his control.
I believe CM was starstruck, and would have been ready to do anything to keep the job. I believe Shafer when he said the guy had no idea what kind of drugs he was giving, even the benzos. I believe he felt it was ok, he played god.
A murder, even under the influence of anger, would have been covered up much better. When you kill someone, you try not to get caught. He had time, they were alone in the room. A premeditated murder, even more. I mean everything point at CM (ok, I'm biased but still). Even his declaration to the LAPD doesnt match the autopsie report. As a dr, that's the kind of stuff you would think about, I mean, you would know about an autopsie being needed and the things you should say.
I believed he screwed up, and he panicked. It's highly possible he removed the missing tubing and put it in his pocket. But everything afterwards screams complete panic to me, running back and forth, calling people who couldnt do anything, at the same time pretending to take care of Michael and hiding as many things as he could. Of course he didnt call 911, he wanted to avoid strangers in the house, because then his secret "treatment" would be known. I believe he was hoping things could be fixed without having anyone from the outside knowing. And there comes the sociopath theory : he put himself first, always. I dont think he cared too much about Michael, I think he was terrified because people would know about HIM doing something he knew perfectly was extremely serious and wrong.
That's also why he played the good doctor part afterwards at UCLA : guilty people try to hide, they flee; not the good doctor who stayed, comforted the family and took care of everything (which we all know is not true). All an act. Like pretending to tell the LAPD where the bags were, because he thought, as Chernoff, that they already had found them.
CM is an idiot, and a jerk. He deliberately put Michael's life in danger, which is inexcusable. He, as a doctor, gave incredible amounts of dangerous drugs to a patient without any monitoring at all. Michael is apparently the one and only patient who was treated that recklessly. The only reason he did it was the money he made out of it. Period.
But MJ being dead, CM's name is dragged though the mud, his cash cow is gone. I dont see what he got out of it. What if he believed MJ would not take him to London after all? What's the point of killing him? Is it better to be in a court room ever day?
If CM actually deliberately murdered Michael, he's the worst murderer in history. Any idiot out there watching TV cold have done a much better job.