Many modern cameras can go well beyond 100fps, though it usually requires restricting the field of view. (That 100fps you are mentioning was probably full frame). So the camera isn’t always the limitation. It comes down more to your sample. If you don’t ever need more than 200fps to capture what you’re looking at, then it doesn’t matter. But if you’re looking at crazy fast things, then that extra 1800fps in the X1 might be useful. It’s a big “might” though, cause in addition to restricting your field of view on the camera, actually achieving 1000fps also assumes that you can get sufficient SNR with a 1ms exposure. That in turn depends on the maximum laser power in your system and the intrinsic brightness of your sample. (Of course, issues of photobleaching and toxicity resulting from the increased laser power aside).
(As a side note here, remember also that getting the very highest frame rates theoretically achievable by a spinning disk requires pretty good synchrony between the disk speed and exposure time if you are to avoid disk artifacts from incomplete frame coverage).
So those numbers about spinning disk frame rate that you were quoting usually refer to the time it takes to make one complete sweep of the field of view (for instance, 1/12 of a rotation on an X1).
I would call those other issues (triggering, simultaneous multichannel, etc) independent of the question of speed… and only you can decide whether they are “more important” to you than the maximum frame rate your system can achieve (again, based on the demands of your experiment and your biological question).
edit: since you mention triggering, it’s worth pointing out that on any of these system, hitting something like 500+ FPS probably assumes that you’re just streaming the camera nonstop, without turning the laser on and off… so triggering is not an issue for speed in that case. Though a carefully triggered system would certainly have benefits for minimizing light dose at lower frame rates (so again… I see that as an independent issue)