the 3 pin relay is required on bikes that are factory equipped with hazard lights.
basically, there are two circuits that use the flasher relay. the one that goes through the signal light switch to either side of the bike (signal circuit) and the hazard lights circuit that feeds all four corners.
on a hazards equipped bike, you cannot use a 2 pin relay as your system will not function correctly.
this guy is from geneva, so he's obviously got the 3pin relay for hazards allowance.
tripage definitely does a 3 pin, and i believe TST may as well. both are trouble free products.