Currently using the 910F 15° & 19°, and I'm very happy with the 5 wood, but sometimes have trouble with the 3 wood as far as solid hits off the fairway.  I was just wondering what the head volume is for the 910F as opposed to the 910FD; I'm contemplating a switch to the FD 3 wood and wanted to know the head size and what, if anything should I know about the relative advantages/disadvantages between the two?

I've done a lot of research on this, but nothing has turned up any direct comparisons between the two, let alone the specs on the head volume. 

Thanks!