The most obvious differences are in their temperament, their behavior; since they are mirrors, in terms of quadra values, functions and even relatonships it becomes tricky.

INFps are more relaxed, not proactive, as if they wished someone would help them get moving to do something. ENFjs are more restless, proactive, hectic.

In behavior traits, following dichotomies.

INFps are merry, compliant and emotion-creating. That means that they will usually be very easy-going when discussing ideas, in a positive emotional atmosphere.

ENFjs are merry, obstinate and construct-creating. That means that it's easier to reach a point where the ENFj cares a lot about ideas and will be unwilling to concede points. Being construct-creating, the ENFj is also more likely to display impatience and annoyance when that happens.