Shaft is the key as stated above, I love the Phenom 60g 3.8 stiff that I was fit for in my new D2. The gain in distance, launch angle and lower spin rate are amazing vs, the others I tested.
I think the feel of a club is also important. Most of us swing a little differently every day. So while fitting is important I think the look and the feel at impact also mean a lot. As I have said hitting fairways is more important to me. If I miss more than 1 fairway a round it was a bad driving day. My group calls me down the middle Bob, among other things.
Shaft would affect the ball flight as others have mentioned based on kick points and flex. getting fit by a quality fitter is well worth it.
NC Bob, I am jealous of your "down the middle accuracy". I am happy to hit 10-12 fairways out of 14. that is a good, if not great day for me. I am picking you to be on my scamble team, that's for sure!!