I don't actually see as much of a conflict between the two in an ENFJ as I do in an INFJ. Perhaps I am wrong, but with an ENFJ I imagine Fe is in the driver seat, so Ni doesn't really get a chance to fully detach. Fe always has a goal that it wants Ni to work toward, so I don't see how Ni can totally become impartial. (I'm assuming a similar thing happens in ENTJ's as well.) Or even if the ENFJ does let Ni run wild she can reign it in whenever she wants.
With an INFJ though, Ni is free to impartially view all vantage points, but when a decision is made it is not impartial in the slightest. It does sometimes seem that after all that Ni analysis is done the final decision is to pick the one that is shiniest, lol. Ni is detached, but Fe cares deeply. It's like Neo from "The Matrix" is teamed up with Mr. Rogers. I don't always understand how the two can work together.