The VX924 is a good monitor for gaming: it's fast, but not very accurate. With a latency specification of 4 ms, that's what you'd expect. Its static qualities are just as excellent, with a well-controlled level of brightness and very deep blacks. But video noise will be a real problem for anyone who uses their PC for moving images - in other words, the majority of users.
The bottom line is that the VP191b/s is a much more multidisciplinary solution, mostly since the gain in latency performance with the VX924 is debatable, as we've seen. The announced 4 ms is more a construct of the measurement method used than it is a true measurement of performance, because it doesn't take accuracy into account.
The VX924 seems to trade off its aggressive use of Overdrive against mediocre performance with movies. That's true for this model anyway, though it's too early to generalize. We're waiting for more monitors based on this technology so that we can compare.
Nevertheless, the approach manufacturers are using for measuring and specifying latency is becoming more and more dubious. There's no reality behind the figures anymore. Before, the claims were excessive and didn't reflect reality, but at least they could be compared. Now we can't even say that. So we'll continue our policy of taking our own latency measurements on all LCD panels (TV sets included).