I'm currently playing a 975D driver. All else being equal (same head speed, solid contact, etc.), how much farther could you expect to hit one of the new drivers?
The difference in forgiveness between a 9745D and most any of the heads on the market now is like night and day IMO. You won't pick up distance on dead center hits, but slight misses will certainly be better with the newer heads. No doubt a launch monitor can make a big difference, well worth doing if you are looking at a new driver.
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Simplicity buffs, see 5-0, 1-L, 2-0 A and B 10-2-B, 4-D, 6B-1D, 6-B-3-0-1, 6-C-1, 6-E-2