It can vary by piece, as Sucellos's enhancing duration is multiplicative with Atrophy gloves and Lethargy feet, despite not being an augment.
With my current gear and using the formula Byrth posted, I should get
haste 2:
sucellos cape - (180+20)*3*1.26*1.78 = 22 minutes and 25 seconds
ghostfyre cape (+19 duration augment) - (180+20)*3*1.45*1.58 = 22 minutes and 54 seconds
From quick testing, that pans out. The durations match and I get 29 extra seconds using the +19 ghostfyre over the +20 succellos with that gear combination.