One of the connectors is much smaller and flimsier the 3 pin and the 4 pin is what is used on most computer motherboards today however some controllers like the Corsair Commander Pro use it and most of their rgb line up other than that i don't think that 3pin is that common, i think personally there is an advantage to 4 pin in compatibility, i know more companies which use 4 pin than 3 pin and that seemingly makes it more futureproof