Regarding the odd success of the prince, a lot of time in situations like this I find it's not the "choosiness" of the fish, but rather some other factor.
For instance:
1. Sometimes it's not that they choose one over the other, but rather that one makes it to them and another does not. Maybe the bigger fly with a beefier hook actually rides the bottom more naturally, whereas another fly could ride too high, or else too heavy and "bounce".
2. Maybe it has nothing whatsoever to do with the fly, but rather the hole itself. Valley is notorious for having long dry spells, and then you come on a hole where everything is set up right for you and you pull a bunch out of there. It could be that it's set up so that you don't spook fish on approach, or your rig is proper for getting the right depth and drift for that particular hole, or that the sun is on the water, or a spring has temperatures more correct, or any number of things.
Fly fishing is full of "other" factors. And I personally believe that fish are less choosy about getting the outward appearance of their prey correct, and more choosy about getting the location, drift, behavior, time and place, etc. correct.
I couldn't tell you how many times, especially on Valley, where I'll take the skunk for an hour or two and come on one spot and catch 5 or 6 on consecutive casts, without changing my fly.