It's hard for me to say exactly, since I don't think I know any sure ENTP's in my life. I do however have an online friend who has tested as ENTP, and he seems to fit the traits that I've read quite well.
From what I've read and heard, the problem between the two is the Si vs. Ne as dominant functions. I really like what this page says about Si and Ne, it really cleared it up for me a lot and showed why there's so much friction between people who use these as their dominant functions.
ENFP Wiki
These two bits are particularly insightful. The first talks about how Si suppresses Ne, and the second how Ne suppresses Si:
I think that right there offers a good explanation of why ISFJ's and ENTP's can have trouble getting along. Basically, what they're looking for in life is exactly the opposite.
When I had long talks with my ENTP friend, I was always amazed and awed by what he was able to do mentally. He basically was on a constant search to improve himself with his knowledge. He was always able to adapt himself in any way necessary for this improvement. If he ever heard a new argument that was better than anything he had ever believed before, he would change his mind if it fit in perfectly logically. He never had any problem making these adaptations...in fact, he relished it. He loved to be proven wrong if it meant it improved his knowledge and thinking.
But I realized through talking to him that I could never do what he did and be happy. My whole life, my existence, even, is based on my past experiences and what I've known. I'm constantly collecting memories and using them to give me peace about the future. I
crave consistency. It's what gives me comfort, peace, and happiness. Without it, my life is nothing but stress and misery. And I long ago realized that my ultimate goal in life is to be happy, because without it, when I look back on life, I see nothing.
It's like I'm in a constant state of preparing for the future. I always want to be ready for whatever comes. If I'm not, I get really stressed out, depressed, and just start losing the point of living anymore.
The funny thing was that I could never rationally explain to him why I was that way, or the value of it. But, thankfully, he still accepted me for who I am, and I did the same for him. We just understood that we could never be like each other and still be true to ourselves.
And the great thing too is we recognized each other's strengths. As I mentioned, I was in awe of his rational abilities, his huge wealth of knowledge, and his ability to always better himself and improve. But he also valued my loyalty, my steadfast nature, and my ability to complete whatever I started and not give up. He also appreciated by genuine attitude and my ability to relate to other people.
And that's where the Feeling vs. Thinking nature comes into play, because ISTJ's also have dominant Si and inferior Ne. But both my friend and I saw the value of the opposite function in that case too.
For me, I learned from him the value in being objective when talking about large decisions that affect everyone, such as political decisions. He got me to realize the importance of putting my own personal feelings aside so that I could understand how decisions affected everyone and to see how to make the most fair and reasonable choice.
But, he also learned from me the value of feeling in personal relationships. He told me about a lot of his own personal emotional issues in his life, and I helped him to analyze his feelings and understand them better. He also learned from me the value of letting go emotionally, to just be silly and have fun for the sake of it, to feel good and just have a laugh. I gave him a comfort to where he could let down his walls and not be serious all of the time. He later told me that this helped him in one of his relationships.
So basically...it's very hard for ISFJ's and ENTP's to relate to one another, and I would imagine that it would be hard for them to be in a relationship or even a close friendship where they spent a lot of time together....because I think they would end up grating on one another over time. However, that doesn't mean that they can't learn from each other and value each other's strengths. If the two types approach each other right, they can learn to appreciate one another and see what they have to offer in life.
He is one of the most joyful people I know. I love his ability to become intensely passionate about something, practicing it over and over until he has it perfect. His enthusiasm is infectious, he seems to live in a world of limitless possibilities. He has a wonderful grasp on people and social situations. Able to instantly put most people at total ease. He has an amazing sense of style and aesthetic and a refreshing worldview. Following through on every one of his plans isn't something he does, but that's just his style and it lets him keep doing what he's doing. He likes to live in the present moment. I find we counterbalance each other nicely.
