It is just basic math
1 int = 0.284 det
1 int = 0.232 crit
1 int = 0.098 spell speed
demon robe = 31 x 0.284 det + 31 x 0.232 crit = 8.804 det + 7.192 crit = 15.996 int total
Augmented Robe = 47 x 0.232 crit + 33 x 0.098 spell speed = 10.904 crit + 3.234 spell speed = 14.138 int total
off stats overall difference = 1.858 more int from demon robe
all stats overall difference = 3.142 more int from Augmented Robe
result = Augmented Robe is better