My favorite Chopin interpreter has been Moravec, particularly his recordings on the old Connoisseur Society label. Some of his work was released on CD by VAI, but Im not sure if this Impromptu was in those collections.
On the Kissin, it's not the same engineer, but Ill tell the story anyway. I got the chance to hear the master tape of a Kissin recording at Carnegie made by Tim Martyn for RCA (I got Tim to bring his console and some of his master tapes to an NJAS meeting at my home last year). For that recording he used a pair of spaced omnis out in the hall, and a three (I believemight have been a stereo pair) mic array over the piano to add presence. Since we were listening to the master tape and had the mixing console, we were able to cut out either of the microphone feeds and listen to just the omnis or the array over the piano. I would say that from your description the recording engineer for the Kissin probably had more of the close-up mics in the mix, while the omnis alone sounded closer to your description of the Hewitt recording (though it sounded about as realistic and balanced as anything I've ever heard in a concert hallTims observation was that Carnegie's acoustics are good enough that you really didnt need anything more than the omnis, and I think that was the consensus in the club after our listening). So I think youre right about the different recording styles, though keep in mind that a recording engineer might have used a number of styles to put the performance on tape, but the producer and the artist have a bigger say in the mix from the mics and the sound of the resulting finished product.