The trade-off is friction and hydraulic shock. Larger surface area means more friction which relates loss in velocipy. But, a large surface area is also going to relate to more hydraulic shock because the ft-lbs are distributed over a larger surface area. I think the right balance has come with the solid copper or copper alloy bullets. They get a nice increase in size and the X's make that nice flower pattern which actually is less surface area than the traditional coveted mushroom. So the flower petals cut more than push and retain their weight and velocipy better. Just an awesome bullet imo.

The two deer I have killed with X's. One was an ill advised shot where I hit him square in the back of knee and it just exploded his knee. F'er bled out in a hurry, I mean a real hury. This years deer was a perfect shot presentation and a perfect shot through the vitals. A hole about the size of my pinky on the entrance and a hole about the size of my thumb on the exit. Inside the vital region was nothing but pink liquified goo. Never recovered the bullet just the critter. The one thing I don't like is that I haven't quite achieved the accuracy I know I capable of with them. I think I need play with seating depth more than I have.

Put that into comparison with the one I shot with NosBT's (90's version). Took three shots, some chasing around, and I F'd up some meat in the process. I'll never do that again.