Magian Trials Impairs Accuracy VS. Evasion

I'm looking at the trials and I keep wondering if there is a mathematical reason for most people going for the +evasion trails as opposed to the impairs accuracy ones other than the +15 lowers accuracy and +20 evasion? Would it make a difference if they were both equal numbers, say +20 each?

It's not mathematical reason per-se. It's because the +20 evasion always works, while the Impairs Accuracy has to proc, and the proc rate of Magian weapons is severely nerfed when dual-wielded. The effect also can't overwrite itself, so it has to be re-proc'd every 90 or 120 seconds or whatever duration and isn't worth swapping the daggers in and out for maximum effect either.

Consistency. Impairs acc isn't guaranteed to proc on a given hit, eva+ is up fulltime.

I wondered this as well Did the defense down lv90gk. Think its a 2 part if not more reason. 1 being alot of people solo or low man most of the time. 2 alot of the lower eva or w/e trials weapons are really low damage compared to stuff u can "full time" I know u can just change out weps or w/e case maybe but the proc effects dont seem to last long enough (neither does the mob) for it to be of much use. But this is just my thought and why I dont use the GK as much but hell -15% defense down is nice even those its on a GK >.<