ethan, are you just talking guards? for bigs its not even close, so im assuming you just mean for guards here. as to which attribute is better, i used to be a guard speed man, but that was also a different day, with a different sim engine. back in the uber press days speed was the king and it wasnt close. now its a much more complicated answer.
in press today, even outside of the relative decrease in the dominance of the press, the relative value of ath, spd, and def has shifted, where spd is no longer by a wide margin the most important stat. i believe its def, spd, ath, without huge gaps between any of the three.
in man/zone, i think most people would agree that ath is at least as important as speed, just from a defensive standpoint i mean, and probably more so.
however, there is also the offensive angle. from an offensive standpoint, for traditional guards, speed is way more important. for pure 3 point shooters, its not close. for solid per guards (can take 3s effectively but only have say 75-80 per in d1) its still speed. i've been trying to study the impact of the various ratings on slashing type guards, which didnt exist in the old engine, so i really have no comparison point from when i really played. but it does seem to me to be very possible that ath actually trumps spd for lp/ft based scoring guards.
the conclusion here is, it depends. you cant just look at ratings and say one is more important than the other, when they are so complicated ratings like this. sure, you can say SB is never as important as ATH for a guard, but these tricky ones, it really depends what you are using the player for. for most defense oriented guards, maybe its ath, for most offense oriented guards, maybe its speed. most. its really more complicated than that and there is no simple answer, IMO.
also just FYI, a 70 ath/spd guard is basically unusable in high d1. they can be decent for NT bound mid majors trying to break into the big 6, but they really have no place in high level d1 play.