The key issue is: there is so much more to speed than speed out of the hand.
To take another example: there's no doubt Stephen Harmison is quicker out of the hand than Andrew Flintoff. Ask pretty much anyone who "hits the bat harder", or who "bowls a heavier ball" (a slightly amateurish phrase, but eventually it'll be phased-out like "an extra yard of pace"), they'll tell you Flintoff. Why? Because Flintoff loses much less pace off the pitch. That's borne-out by the scientific facts, too - look at the (all too rare) graphics showing the pace of the ball as it travels down the pitch. Some pace is lost through the air (that's obviously equal for all bowlers, though it will of course vary according to conditions in the air), but a lot is always lost off the pitch.
Often, the amount of pace not lost off the pitch is far, far more important than the pace out of the hand.
Phrases like "bowl a heavy ball" refer, of course, to the amount of pace lost off the pitch. Like I say, I'm not a fan of them, because they de-scientificise the matter, make it seem a bit mystical and undefinable.
However, the only explanation for shorter balls measuring slower (given that the speed displayed is the first speed measured as the ball leaves the hand) is the difference in direction - shorter balls obviously take a different course to fuller ones. Or it could just be down to misperception. I don't know if there's been a statistical research on the matter.
Judging a ball, however, by the reaction of the batsman remains a stupidity. There are all sorts of reasons why the batsman might be rushed. He might not have picked the ball up instantly. He might have got something in a tangle (pad, wrist, elbow, whatever). Something might have got into his eye just as the ball was about to be delivered, too late to pull away.
The most important point of the matter is that there should be more than one reading. The most informative, for mine, would be three: speed out of the hand; speed off the pitch; time between ball leaving hand and reaching whatever point it hit the bat.
People make speed to simple; yet at the same time they perpetrate pure folly in attempting to know better than the instruments.
As for wicketkeepers standing-up, there are all sorts of factors, aside from the skill of the wicketkeeper. Bounce is obviously a key, added to pace - bowlers getting more bounce are much more awkward to stand-up to than those who don't.
That has far more to do with the Watson-McGrath question, and many similar ones with different bowlers.
