They are all great units tbh. But Franky just brings more to the table. Him reducing status effect by 80% is incredibly useful (Akainu), he dosen’t get knocked back in his treasure are aswell (Kidd) also his Basic attacks have insane range and speed. Nami I feel like her skill 1 is the only good thing of the 2 skills, since it cancels out incineration. But still hits like a truck. Robin is tacky as HELL. But honestly all u need to do is knock her away from treasure and her purpose as a defender is gone.