BDK's planning exercise and the follow up made me grab Michael Stean's classic "Simple chess" again. I especially felt the urge to read what Stean had to say about space and the advantage it is to suppose to offer. And again I was impressed by the clarity of his explanation. This a small part of his treatise of this subject:
Space is not an easily definable or recognizable concept. The visual impression you obtain by glancing at a position and estimating who seems to have the lion's share can be misleading. The following is nearer to the truth. Any given pawnstructure has a certain capacity for accomodating pieces efficiently. Exceed this capacity and the pieces get in each other's way, and so reduce their mutual activity. This problem of overpopulation is easy to sense when playing a position, it "feels" cramped. To take an example, compare the next two positions.
They do, of course represent the same position, but with two pairs of minor pieces less in the second case. In the first diagram black is terribly congested. There is no way he is ever going to be allowed to play b7-b5, while alternative methods of seeking some breathingspace by (after due preparation) ... e7-e6, or ... f7-f5 would compromise his pawnstructure considerably. White on the other hand can build up at leisure for an eventual e4-e5, safe in the knowledge that as long as he avoids any piece exchange, his adversary will never be able to free his game.
The second diagram is quite a contrast. The size of blacks forces is here well within the positions "capacity". As a result there are no spatial problems at all and black can very quickly seize the initiative by ... a7-a6 and ... b7-b5 or even by ... b7-b5 as a pawn sacrifice, e.g. 1 ... b7-b5 2 cxb5 a7-a6 3 bxa6 Rxa6 with tremendous pressure. We see from this pair of positions that blacks structure is very good, but his capacity is small. Visually white has a spatial advantage in both cases, but in the second the eye flatters to deceive. In fact he is grossly overextended. A vast empire requires an army of equal proportions to defend it.
I have nothing to add to this, besides a glance at the position BDK gave us in his planning exercise.
Indeed, white has space? But why should this be an advantage, considering the explanation given above? It seems to me that blacks forces are will within the capacity of his pawnstructure