Good point.INTPs and ENTPs are fairly similar in their temperaments. They only really differ in that one is much more calculated (INTP) than the other (ENTP) in their interaction/planning thanks to that god damn Introverted Sensing function that ENTPs pretty much lack almost entirely...
I get INTP as a result in all MBTI based tests, but, when I did the cognitive functions test, it came out as ENTP, which is interesting.
The thing with the 'calculated' bit can at times manifest as 'paralysis by analysis'. Every type has its positives and negatives. What we need to do is maximise our strengths and operate from there, and mitigate our weaknesses.