I got a great question via email today. Paraphrased: "The two MCMs I know, know SQL Server to a depth much deeper than the videos suggest you need to know. What's the real depth that you need to know to pass the MCM?"
I'll illustrate it with my SQLOS video. Back when the Microsoft Certified Master class consisted of a 3-week in-person event in Redmond, most of a day was dedicated to SQLOS. My video, on the other hand, is only 24 minutes long. Think of SQLOS as a pool. I dove off the diving board, went straight down CPU scheduling, and touched the bottom of what you need to know on that one particular area of the pool. I came back up and got out of the pool – but I didn't swim a lap, and I didn't dive all the way down in all of the parts of the pool. I didn't touch memory clerks, lock management, or the buffer pool, for example. That's where the recommended reading list and SQLskills training courses come in – there's much more you need to know, but we don't have videos to cover all of it. Think about it this way – there's only 40 hours of videos, but SQLskills offers four weeks of MCM training. If you could learn everything you needed to know in 40 hours of videos, we wouldn't sell a single seat of training – but we do.
Now, about the depth of MCMs you've interacted with – I can go on for days on CPU scheduling. I think it's one of the sexiest topics out there. Whenever Anandtech publishes their analysis of an upcoming processor, I pore through it repeatedly. That's one of my strong points – but I can't cover every topic to that depth. There are plenty of MCM subject topics that I understand well enough to be a Master, but I don't understand well enough to teach at the Master level. Frankly, there are even a few topics that I don't understand well enough to be a Master <cough>CLR</cough> – but thankfully you don't need a 100% score in order to pass. When you see a Master presenting, and you see their level of knowledge on that topic, remember that it's one of their specialties.
Finally, not all the areas of the pool are the same depth. On relatively-new features with minimal adoption like Policy-Based Management or Resource Governor, you may not need to know the internals of how it works inside the engine, but you have to know the externals well – how you access it and manage it. On time-tested topics like how a table is stored on disk, you gotta know internals, even the stuff that isn't exposed to end users, because that hasn't changed dramatically in a decade and it impacts everything you do.
I hear what you're asking, for: you're asking for depth markers on each area of the pool, and a clear definition of what that depth means. I wish it was as easy as a single integer, like "The Clustering module is 2 years of experience deep," but we both know that 2 years of experience means very different things to different people. If I had to boil it down to a single integer per module, I would probably try to use the number of projects you've done with that particular feature, but even that doesn't work with things like storage internals. Over time, as the certification becomes more mature, I'm sure we'll see skills checklists and study guides just like we see for the MCITP. Until then, the best thing I can point you to is the SQLskills Immersions training agendas. Take each week of training, look at the modules, and look at the time allocated. Think about the depth we go to in a given amount of time on the free MCM videos, and we go to that same depth across each module in person. For example, in the Performance Tuning week, one of the modules covers SQLOS, and each module is roughly 2-4 hours long. You saw 24 minutes on CPU scheduling – now take that same depth across the other topics in that module.