I guess I should chime in here.
1) Fabian, I think you're selling yourself short if you don't think you are one of the very best. But I know how you feel. When I first made it to the top, I did so on the back of a ridiculously good streak. I think I jumped close to 5 levels in around a week. So I fully expected myself to fall back to the high 40's any day, and yet it's been some time and well, here I am. Actually, I still kind of feel like that. I make mistakes, some subtle, some glaring, all the time. Though I do think recognition of what constitutes a mistake is something high level players are very good at.
2) In response to your actual question ... I really don't know. But I guess I can add a little to the discussion.
The biggest thing I notice about this thread is the perceived division between Big Money strategies and Engine strategies. But I feel this is far too simplistic. We have engines with villages, engines without villages, engines with major trashing, minor trashing, no trashing, engines with alt VP's, engines with attacks etc. Even big money can be decomposed along many of these lines.
I think the critical thing to understand about each of these scenarios is how fast they make the game. And I think everyone understands this, but it bears repeating. Some strategies need a slower board to shine. Some shine in faster ones. Some shine when there are attacks. Some are crippled by attacks. The difference between a level 40 and a level 45 is a small one. Most boards have a fairly dominant strategy which lvl 40+ will pick out quickly enough. In these games there is no difference between the two skill levels. The difference comes when the standard strategies we've seen dozens, maybe hundreds of times, get even a small wrench thrown in. The lvl 45 player has to be able to discern how that wrench can add even percentage points to his or her win probability.
I guess it boils down to this: those extra percentage points which take you from 40 to 45 require some combination of intuition and experience. So that might sound kind of vague, and I guess it is. And perhaps that isn't actually that insightful. But like I said before, I don't really know the answer.