> there is a well understood principle that fair auctions will out-compete unfair auctions in the long run

In what sense? If anything, the market failure of non-competitive markets almost implies the reverse: power prefers unfair auctions.

> whether that concentrates wealth at the top is a consequence of a lot of other factors

Correct. (And as an aside, sealed-bid auctions are particularly good for small bidders or bidders in an adversarial market, the latter for the same reasons a secret ballot is better for small parties.)