This is why I won't go for Stewardship. Sometimes, the penalty for having three duchies can be negligible, other times, it will cause revolts every five years. Specially in large, multicultural kingdoms. I find that the most useful thing is diplomacy; learning boosts tech, but nothing so impressive - and that a part of the game that is not that important anyway - but with a high diplomacy ruler, you'll have an easier time doing anything.
If you are a King+ and have a demense county within a de jure duchy and give that duchy title out to a vassal they do NOT get your county as you hold it directly. Indeed rather than collecting a whole duchy as demense I will pick the best county (6 holding, coastal, etc) to keep as demense and give the rest to a vassal to manage. Yes it does mean that the Duke will have that "desires county" modifier, but if he only has two 4-holding counties I don't really care if he gets out of hand because I will easily crush him.
I ran the same game through once with Master Theologian, Midas Touched and Grey Emminence.
Master Theo: I have no clear evidence that it matter as I don't know how the mechanics of tutoring work, but I sure seemed to get heirs will really good statlines. Also with such a high learning I would often educate my major vassals' heirs, avoiding intrigue vices and trying to get as many of them with +mentor, culture flip and content. I don't care if my vassals have good stats. I care if they have attributes that are not compatible with mine or likely to make them troublemakers. Note that most of my Master Theologians tended to have decent stewardship and 10+ demense size because most of the virtues lend to good stewardship as well. I could not tell much one way or the other whether Tech was better. Frankly it seems like the ahead penalty keeps everyone from gaining too fast no matter how much you focus on it. (Not like EU3 where you can rapidly get ahead or fall hopelessly behind tech-wise.)
Midas Touched: Most subtle of the three in the sense that you have to start really grabbing max demense right away for it to matter as much. In my opinion only, Stewardship is a very bad thing to have very low, but having it very high did not seem to make a huge difference in monthly income and therefore was only useful if I kept demense maxed out--which caused succession issues. Also if you start out Gavelkind without Free Investiture you are going to have to assassinate your extra sons for this to be helpful. And, well, that's just a bit beyond the pale
Grey Emminence: The only problem with this trait is that once short reign has worn off I don't have any interesting rebellions and as long as I hire a good spymaster and keep him happy I can squelch plots fairly well. Um. That's awesome. Perhaps not relevant if you are small, but if you are mid-sized or larger it is a huge difference and the improved relations with the church and vassals in general helps with income as well.
Note that I try to marry spouses with stats that help mask my weaknesses. The only exception is Intrigue. Sorry, I don't want a wife with a 20+ in knife skills.