INTP's tend to be more interested in developing theories while ENTP's tend to be more interested in developing projects.
INTP's tend to be a bit more aloof, while ENTP's tend to be a bit less orthodox.
ENTP's can seem reckless at times, while INTP's can see to be completely emotionless at times.
And yet both ENTP and INTP really share these traits. It's really more about degree.