I really don't like grappling with a gi (the pants are ok but I don't like the jacket)...
If I miss the armbar I usually counter with a keylock or DWL (since one foot in on the ground you just have to jump way over him
) or go for an arm-triangle (since the arm is already in his face I smother him with it while I go for the figure-four)! The choke works great on big guys!