Ashkenazy is for many the top choice in Rachmaninov, and I might be inclined to agree. But while these accounts with Haitink from the eighties are interesting and strongly recommendable, I don't think, in the end, that they in any way replace his earlier accounts with Kondrashin and (in particular) Previn. What are the main differences? Well, as could perhaps have been predicted, the tempi are slower and mellower, but the textures are darker as well, and that isn't obviously a negative thing - especially, I'd say, in the fourth.
Ashkenazy mastery of the piano parts are never in doubt. His assured playing is never less than impressive, and the darkness Haitink draws from the orchestra (sometimes a little overbalanced and favoring the dark strings) makes for a surprisingly engaging perspective. The Concertgebouw Orchestra is, by the way, awesome - not only in the darkly dramatic parts, but also in their ability to create nuances and shades in the more lyrical parts.
That said, Ashkenazy and Previn are overall a more obvious first-choice in no. 2. But in no. 4, the situation is different - the dark, melancholic hue acquired by the main theme of the first movement, for instance, is utterly convincing. And the grimness and robustness of Ashkenazy's playing (and the dark strings of the Concertgebouw again) present this work in a far more somber light than we are used to - and it makes perfect sense. Sound quality is open, but a little cathedral-blurry and more than a little digital. All in all, this disc is strongly recommended.