I'm not going to bring science into this, just my experience. I play nothing but ivory ferrules. I do everything with em. Break, jump, play........... I have yet to break or crack an ivory ferrule. The good thing about having a lathe is that I can put a new one on, so I fire away with confidence.
I played the standard ferrules or whatever came on the shaft before I started tinkering with cue making. I didn't know the difference, and actually didn't really care for ivory.
When I first tried it, it was unfamiliar and produced inconsistent results. I experimented with different tips to adjust to the ivory, but the ivory seemed to just deflect more. As more time passed, I tried other shafts with ivory ferrules, and then went back to the fiber ferrules, and after playing ivory ferrules for a while, I noticed a difference. The fiber ferrules provided a dead hit. The ivory provides a much more lively and pingy impact thus resonating more. Now, the ivory may deflect more in comparison to the fiber, but I can't tell you how much. All I can tell you is it ain't a lot. The way your brain becomes accustomed to things over time, it is much more worth it to play ivory ferrules than anything else. That's just me though. I still have a couple shafts with a mason micarta and I think those are nice too.
As far as 3/4 ferrule I've played that too, and it does deflect less but I personally like a ferrule that is a normal 1" I don't mind whatever deflection there is because I play just fine with what I use, which is a radial pin dufferin conversion. I personally think all that LD BS is a bunch of BS. To minimize deflection is one thing, but to depend on it is totally wrong. I believe in hard work spent on the table will enable you to use any shaft with any ferrule or tip with no problem at all.