There aren't a lot of guys that have a plus plus change-up in the majors. For that matter, there aren't many at the pre MLB that have a plus plus change-up. Down to the college and HS levels there are even fewer and fewer. At the pre HS level you may see 3-4 pitchers all year long that have a great change-up.
I was saying earlier that we once played the best travel team around and that we would start them out with a first pitch CU and it would get in their heads so bad that you could throw anything after that pretty much - mostly fastballs and then come back occasionally with the CU deep in a count and get them to strike out.
I will agree with you that a live plus fastball in the 90's is something special- a rare talent in and of itself! But, it is my opinion that if a pitcher also has a plus CU to go along with his hard live fastball that batters fear the CU the most in their at bat. This is why I believe most batters wait and watch for the fastball. They analyze when a pitcher is most likely to throw their fastball and then step into the box with a predetermined idea of when the pitcher is going fastball and then swing.
The art of the pitch is its - what I call "magical deception". Here is why I prefer the CU as the best pitch in baseball-
The eye is trained to pick up the initial velocity of the torso, arm and hand motion. At this very early stage the mind predetermines the exact future moment that the pitch will enter the zone ready to hit. A great CU will be thrown on the same exact plane at release as the fastball. The mind seeing the velocity of the arm as the same as the fastball will automatically trigger a subconscious timer based on the speed of the arm initially and then later it recalculates. If a CU is thus thrown on the same plane as the fastball, the odds are that the mind will automatically trigger fastball swing and thus why hitters will look so foolish when after they start their fastball swing they readjust and try to slow the bat down.
Timing a great CU out of the hand is thus impossible for the mind to calculate as every visual trigger says "fastball, fastball, fastball". It is that fear that screws up a good hitter. Good hitters are conditioned generally to hit fastballs because it is the easiest pitch to calculate actual velocity out of the pitchers hand at release. We did a test with batters who would swing hard on the change-up. Instead of switching off and on with the fastaball we would just have the pitcher throw a harder CU the very next pitch- and sure enough the batter would swing even harder the next pitch convinced that it was the fastball. We could strike out batters with this method on three straight change-ups with each consecutive CU thrown slightly harder than the last. It told us as coaches that the batters mind must always think fastball out of the hand and then readjust after some time from that moment. The mind doesn't like to think oppositly because that is where he gets burned- if he thinks CU and it is the fastball he never gets the bat around.
The magic trick of the CU when thrown perfectly is that by the time a batter realizes it isn't the fastball it is almost always too late to readjust and make good contact. If they do recalculate it is more of a defensive type of swing that leads into lots of pop-ups or grounders.
One of the problems that exists is that in my opinion not very many pitchers at the pro level know how to effectively throw a CU. I went to a MiLB game last weekend and of the 6 pitchers I saw, only one had a good enough CU that I honestly couldn't tell what he was throwing until the ball was over halfway to the plate. The other pitchers would change their delivery just enough that you could tell right at the moment of release if it was the CU or not.