I worked the D3 better, and had less spin.  I don't know the physics behind it, but I would guess it's impossible to hit a golf ball with absolutely zero spin.  The D3 spun less and I found my fade was a nice little fade, and my draw was the same.  Maybe it's easier to control the spin.  I think if you have too much spin you'll duck hook and slice like crazy.

Thank you to all who answered.  This makes sense.

The lower spin is the backspin, more backspin means less curve. I'm sure you've heard use a higher loft driver to help hit the ball straight because it causes more backspin.

The spin is in 2 parts, backspin and side spin, the ball doesn't spin 2 different directions at 1 time, the spins merge together to make 1 diagonal spin. The higher the backspin to side spin ratio the more up and down the spin direction, the lower the backspin to side spin ratio the more side to side the spin direction.

I hope I didn't confuse you more.

Basically, more backspin means straighter, less backspin means it will be easier to curve.

Great answer john h. i think mine was alittle to long winded and probably far more confusing

Maybe read the second paragraph first hahahahahah. i got alittle lost on my self

No this isnt a contradictory statement although i can see how. the spin refers to bottom to top spin or back spin. The club design of the D2 with its weight distabution is designed to take mis-hits and absorb the impact and provide the best out come for a straight hit. it also promots getting the ball up for people who have a problem with this. the D3 is designed to give more of a specific punch and react more strictly to the input. Also if you look at the club faces side by side you'll notice the d3 is a taller more narrow face compaired to the lower profile wider face of the d2. This low profile wide face reduces side spin for more straighter shots.  The D3's smaller head taller narrower face is designed to promote more reaction to manipulated shots. Less forgiving on off center hits but still lots of raction.  What dose this mean.  on a pure center face hit with a fitted club on both syles over all distance should be relitivly the same. off center if you hit a power fade you would get more distance from a d3 in theory. thats of course both clubs fade. a d2 should help cut down on power fades. In other words hiting a power draw or power fade these things are easyer to manipulate with a d3 most people that hit D3's like my self rarly try to hit a Straight shot were always either tying to hit a fade or a draw. sometime we try to hit straight but were tying to work the ball more. the D2 tryes to correct these things. you can still work a fade or draw with d2 but its harder to hit a cut fade or cut draw with one. if you want to know what a cut draw is off a driver its a shot that only moves about 10 to 20 yards from right to left.

Spin agine sorry i got off track and probably babled on to long.  By creating a club that increases back spin on ball it makes it more difficult to generate the left to right or right to left spin. Now then you might say what do i mean ok. math says this club is moving 90ish MPH back to front on the target line. Perfect swing its pure back spin right. know the on a fade or slice swing. your front to back is still 90 but your right to left is only about 15 or so. (not exact numbers only for example). So with this number if you hit this ball with a pure blade all the energy is transferd directly on condact. this is why blades slice worse than cavity backs. A Cavity back absorbs the inital inpact. On the rebound from this impact when its transfering the energy to the ball its tying to send the ball back with the most energy in the direction the club is traveling this being back to front not right to left. These are based on fractions of angles not huge miss swings.  if you have a sever slice swing your going to slice no club will fix that. Now then in creating a more forgiving club like a cavity back your moving weight to perimiters this creates larger amound of spin. this is in the phyisics of the club you would need graphics to further explane it.  Same as in the driver longer deeper faces are like cavity backs and smaller more compact heads are like blades. Im sure RC has something about this and can better explane it.

P.s. the ball almost  always spins bottom to top. it might be bottom right to top left or bottom left to top right but its almost never right side to left side. if you did this you just lost your ball probably.