I don't know that straightforward data on this will ever be forthcoming. And we can produce theoretical arguments every which way, not entirely unlike how classical philosophers were able to prove, through reason alone, that objects in nature tended to only travel in perfect circles and straight lines, and never shapes like ellipses and parabolae, and probably produce about the same volume of useful epistemological output in the process.
I'd think that the more interesting thing would be to try and find some proxies we can use as an ersatz empirical test. For example, what about ad prices? If personalization based on tracking really does work better than other forms of ad targeting, then one would expect that that difference would yield a noteworthy difference in ad prices.
In short: If it really works so well, then you'd expect personally targeted ads to cost significantly more per impression than ads that use content-based targeting. And I'd assume that that information is reasonably public.