CG's right!
The four blade will cut a square, whereas the three blade will cut a triangle. The square, although it appears smaller, actually has a larger area than the larger triangle. Larger hole = quicker blood and air loss. The smaller profile of the four blade should fly better, too. I always avoided using them, thinking they were too small, until I found this out. Now I'm looking forward to using them this year.
Trebark

Become one with nature...then grill it.

All this extra size is great....as long as you aren't giving up penetration. In MY book, 2 smaller holes are better than 1 big one. That goes double if you actually have to do a blood trail. When shot from a tree stand, if you don't get an exit wound, you might not get a very good trail (on the other hand, you might). This seems to be a reason the 4 blade heads are normally quite smaller than 3 blade heads. (1" vs. 1 3/16&quot.
That said, I'm going 1/2 way. a LITTLE smaller head (1 1/8&quot but still 4 blades. (just cuz the ones I'm getting don't come in 3 blades)