There is really not a lot of difference between xx78s and xx75s. xx75s are just a little straighter but I doubt even very good trad shooters could measure the accuracy difference. I believe the difference in strength is xx75s have a yield stress of 96,000 psi and xx78s have a yield stress of 102,000 psi., or something like that. Unless you are bending up a lot of arrows stump shooting or spending lots of money on dangerous game hunts I doubt the price difference is justified. Try xx78s if they interest you, but if you can not get them in an arrow size the works good for your bow and shooting conditions I would not worry about it.