At the moment I can see white's strenght lie in the d6 sq
Who is better and how/why?
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It's complicated and hard to tell. I think that, if White does nothing, Black will attack his center (with e5, maybe a b6 after that). Black's knight is awful on b8 and it has no good squares to go. I would try Nd6+ Bxd6 cxd6 and that d pawn will be quite painful for Black. Other moves should be OK too. You should take however what I say with a bit of salt, the position is difficult and I am too weak to fully understand it.
By the way, there are a lot of such advanced lessons in Chess Mentor (look for the courses written by Silman).
What are each sides' strengths and weaknesses? Is either side decisively better and based on which factors?