When I was looking for a job and was concerned about where I'd end up, a wise friend said, it'll be one job in the end. You only need that one to work out and it will likely surprise you.
In relationships too, it's one that needs to work out in the end. Everything up to that point is up for examination from every angle possible, including type.
With types and relationships, friendships or romance, it really helps to know what the typical pitfalls are. We identify with a type for a reason and that does imply a common set of traits. ENFPs and ENTPs are not necessarily the anti-Christ for each other. I don't find that to be the case.
I do, however, find some common pitfalls in this pairing:
1. Immaturity in either type comes out in different ways, one fails to acknowledge the importance of objectivity while the other fails to acknowledge the importance of an internal value system as a guide. Both can be fickle and manupilative in different ways - one with histrionics or emotions more generally while and the other with a poor moral compass or emotional distance. The issue is immaturity but the pairing of two immature people could be disastrous when they belong to these types because they play off what each finds least attractive in the other.
2. Emotional unavailability: Both could have problems with commitment. Also could manifest as emotional distance in the ENTP and a real reluctance to explore the emotional side and the worst insecurities in the ENFP emerging with constant prodding of the emotional side in the ENTP.
3. Different commmunication styles: So much in relationships of all sort is said non-verbally and small misunderstandings could lead to bigger problems when either/both are not good or willing communicators. Avoiding confrontation doesn't seem to be limited to Fi or Fe.
Eventually, we fall for people who meet certain needs. I don't see why ENTPs or ENFPs can absolutely not do that for each other (sorry about the double negatives). There's a lot that we share. I read
here some time ago that a successful ENTP-ENFP pairing often refers to each other as best friends. That's pretty attractive.
I LOVE being challenged intellectually and surround myself with people who are willing to do that. Why wouldn't I want to do that in a relationship? Besides, there's real chemistry when Ne meets Ne - it's a beautiful thing in so many respects.
As long as the person was willing to listen and had, as SS has mentioned before, a basic sense of humility which is a necessary virtue for me...many ENTP virtues are very attractive.
At the same time, from an ENFP's perspective, I don't want to be someone's project for improvement either - for greater or a certain type of ambition, a more rational approach to relationships (I compartmentalize well, thank you) or a decreased interest in scaling the emotional depths of a relationship. ENTP or not, this wouldn't bode well for me.
So, as there is only one relationship that has to work out to disprove this rule, I'm not willing to exclude the possibility of being surprised by this pairing as any other. In the long run, a foundation of mutual respect, openness and a willingness to work on a relationship seem to go much further than type based matches/mismatches.
