i dont see a difference between infjs and intjs?

so i dont see a difference,they both seem the same,in terms of logic,and feeling,fi in intjs gives them a feel and ti in infjs gives them logic,so they both cancel each other out?,infact intjs seem more abstract minded to me,because they have ni-fi while infjs have ni-ti so even tho intjs have te and infjs have fe those are external functions,and the internal thoughts of an intj would be much more abstract?