Q. What is this Big Idea, the keeping the top hand on the bat?
A. I'm old enough to remember the firestorm of Charlie Lau debates... Lau taught George Brett, Frank "Big Hurt" Thomas, etc. that they'd have more power releasing the top hand and that turned out to be correct.
Ken Griffey Jr. had the most beautiful top-hand release you could even imagine. Edgar released the top hand. ARod fashioned a logo out of it.... You probably do get more power with the longer followthru.
We're back to that 10 o'clock to 2 o'clock pitch shot in golf. Better control. "Casting" the barrel at the pitch does allow a batter to keep his head down on the ball naturally, and allows a longer arc. But the 10-to-2 sports movement does engage upper-body strength and does improve hand-eye coordination.
Q. Does it cost a lot of power or a little?
A. We're talking a fairly subtle difference if you ask me... You can swing hard with bat control. Ty Cobb had two split hands. Babe Ruth kept the top hand on. I got two words for you: MIke. Trout.
Bet you the Mariners got the idea from John Jaso. Had you noticed that Jaso actually splits the hands on the grip now? Blowers pointed it out. ... anyway, you know how influential John Jaso is now. They've got everybody learning from Jaso.
Hey, some guys are strong enough at 90%. If Justin Smoak can crush a Tyler Sheppers fastball 420 feet to center with two hands on the handle, I'd say yeah, take the extra bat control. Funny thing is: Smoak's hitting the ball farther with the cut-down swing. See Saunders, Michael.
Like it, love it, or gotta have it size? On the two hands thing, Justin Smoak anyway, we'll go with Gotta Have It. Later on in his career he can revert. For now we'll enjoy watching him cover pitches.