Kinda tough to statistically back it up. I generate what I call 'Advanced Total Driving' which factors in Fwy %, Driving Distance and Average Distance to Edge of the Fairway (when drive misses fwy). It's a formula that I use to factor in what correlates most to scoring average. Problem is that the Edge of the Fairway stat only goes back to 2008 IIRC.
I think you're better off at measuring approach shot statistics by looking at proximity to the cup averages...which only go back to 2002 or so (IIRC).
Then one has to factor in what qualifies as 'the greatest ballstriker on Tour over the past 20 years.' Lehman has played that long on the Tour...non-stop. Somebody else may have played on Tour for 5 years, struck the ball brilliantly, but had no putting and no short game and lost their card and never came back. So do you factor in career length or actual ballstriking for when a golfer was on Tour. And if it's the latter, what's the 'cutoff point' so we don't get one-year wonders (i.e. Jason Bohn in 2009 who had a phenomenal ballstriking season and is nowhere near as good after that).
One guy I would consider....David Toms. He's been really, really freaking good for a long, long time.
Somebody with a shorter time would be probably Charles Warren or Boo Weekley. We have stats to back up those guys and they both hit it very long. In fact, if it weren't for statistics we probably would never have heard about how great Warren strikes the ball. Same with David Toms who in my estimation has always gotten credit for his putting when his ballstriking has generally been superior.
So it's a typical Brandel statement...blurting things out and having little in the way of backing it up or sound reasoning.
3JACK