But wait, what about Ti - doesn't both INFJ and INTP use Ti (as you might think)!? Well, let's shift perspectives here and talk about ISTPs in relation to ISFJs and ISFPs. I bet that that at least 9 out of 10 ISTPs would relate better to ISFP than ISFJ, despite how ISFJs and ISTPs both use Ti.
Certainly there's many more things to factor than simply cognitive function comparisons. I'll let you reason the rest out.