Generally you always want 1 on use and 1 proc/passive trinket and H Forge edges out the N Horn because of the huge strength difference, even tho the mastery proc on Horn is better than Forge's proc for us.
As far as I know, Forgemasters is pretty mediocre compared to your other options in the same tier. Since it's a tier higher though, go with it and vial. If at any point you get a heroic horn of screaming spirits, I would replace forgemasters.