hmm. need all of them to some degree.
but for creating an elite scorer, i think id prefer
99 ST
80 PE
80 SP
as opposed to having one of the others at 99 and ST at 80.
I think I would put PE third of those three in importance of having 99 vs 80 at d3.
*********important note: when i try to create an elite scorer, i purposely create a very weak schedule, so 80 SP is a stud in nearly every game I play. If you are playing an elite schedule and/or focused more on NT than scoring champ (as I assume 99.999% of you are) then 99 SP may be so important in terms of creating mismatches that youd rather have that than 99 ST.