Just wanted to thank everyone who contributed to this very helpful thread. Several years ago I began performing with a local orchestra and soon found myself playing harpsichord parts for the first time in my life. My initial focus was on learning to perform these parts correctly, and of course the more I listened the more I became dissatisfied with the stock harpsichord sound in the Casio PX56. I'm primarily a commercial composer, and wanted to bring the realism of the kinds of VIs I'm used to in the studio to the stage.
The orchestra shut down for the pandemic, so I used that time to switch to a Roland RD88 and get comfortable with MainStage. Then I began searching for a harpsichord, which led me to this thread. I already owned the CineSamples and Berlin Harsichords, both of which are great in the studio. But I quickly ruled them out for live purposes, because even their close-mic positions have a fair amount of room leakage. I wanted a drier sound so that the any ambience is produced naturally by the hall, as with an acoustic harpsichord.
Based on the advice here, I purchased the Soniccouture collection and the Xperimenta. The Soniccouture harpsichords are both excellent, and provide a great deal of sonic range. But in the end (at least for our recent performance of Corelli's "Christmas" Concerto) I wound up preferring the Xperimenta. All three are wonderful, but the Xperimenta has a personality that makes it really fun to play. In particular, there's something about the key-press samples that give the instrument a "woody" quality and a slight, satisfying "thump" so that you feel as though you're playing an acoustic instrument. The sound of the Xperimenta may not be quite as refined as the Soniccouture instruments (which I might well turn to in other musical situations), but I think its unique characteristics are part of its charm.
FWIW, I did seriously consider the Pianoteq as well. In the end I decided against it, primarily because I was satisfied with the Soniccouture and Xperimenta products, but also because I didn't want to spend that much money on what is mostly a piano library (and I'm sorry, but I'm not that wild about the sound of Pianoteq pianos).
Anyway, I appreciate both the advice offered here, and the efforts of the developers who worked so hard to create these detailed instruments.