Um, I don't know much about Socionics, but from the information on this forum I gathered that Socionics INFj is in fact MBTI INFP...

If Socionics ESTp is still an MBTI ESTP, which I'm not sure about, that would make it the same kind of duality as INFJ/ESTP in MBTI, which is considered the best pairing by many.
Personally, I've observed that the anima/animus often really attract each other and sometimes can work very well together (just like you and your wife), but sometimes the relationship ends up being extremely challenging. However, I'd say that neither is actually the result of MBTI.
As for INFP/ESTP... I really like ESTP guys as friends; they're probably the closest to my archetypal image of a "brother". It's fun, it's natural, but there's no romantic attraction. I cannot imagine going out with any ESTP I've met so far, because ultimately I look for a potential soul-mate or mind-mate in a relationship, and I haven't had this connection with them.
I think that duality provides the smoothest relationship of all intertype relations. It doesnt mean that 2 types will always connect on everything and that interests, etc must still align. You still have to have the commonality that pulls you together, without that you have 2 people who can become physicologically close with ease when it is needed, but drift apart when its not needed.
The best way to explain duality is for me to tear apart my relationship with my wife(ENFJ) and my relationship with ENFPs. Me and my wife really enjoy each others company, but there is a point where we tend to push a button that bothers the other person. I wish I could honestly tell you why, but I have the hardest time putting my finger on why what she just said bothered me and vice versa. To bring in a real life example that just happened. My wife was in a good mood and made a comment about her shoes. I then called them clod hoppers and it really bothered her and killed her mood. The fact that I didnt like her shoes, but I forced things to be dug into which allowed me to explain that I actually like those shoes, those are the shoes I generally pick out for her to wear, and it reminded her that I really do like them, but it still left that feeling inside her. I only made that comment because the heel is big and thick

. The thing is that knowing how Ti and Ni work I can see exactly why this happened, but it doesnt tell me what the issue is, I have to rely on her to open up to understand. What came about is that someone else she knows calls them that and doesnt like them. So even though I have always liked them, it hits her at a deeper level that I didnt understand. If you read the description of conflicting relations it says specifically that things are just under the surface that seem to cause problems.
One a side note our conflictor and our dual pair in socionics are actually really close on alot of levels and if conflicting pairs were so bad and horrible then why does it also state that we are initially attracted to our conflicting pair? Their is something their, but there is also something under the surface that just seems to cause this distance and you really got to get to the core of it.
On the other hand with an ENFP and my interactions, I seem to be able to turn around and comfort them. For example I can rant to my mom about my wife. There is a commonality and my mom will always bring these up and I can honestly see where they are coming from, but their is also a difference in the way each person handles things that are different. My wife and my mom disagree big time in the way each other handles problems. I have talked to my mom about this and their is a kinda envy, but a dislike at the same time in regards to how she thinks my wife handles problems.
Their was a particular issue was between my sons NFP teacher and my (ENFJ) wife. The NFP teacher tried everything she knew and turned to blame outside of her control. Didnt come across to my wife so good and she became defensive and things kinda spiraled down hill. Now when an ENFJ director came in it was like battle of Fe and things were able to be brought up in a different fashion and the tension was better managed. It became a much more healthy argument. I didnt really do alot of the talking. I could understand both my wife and the teacher, but at that point I didnt feel like their was anything I could do either way. To get the teacher to back down would require me going against my wife. To go with my wife would cause the teacher to feel like she was ganged up on and hit a defensive mode which she already felt ganged up on.
ok, im lost now with where I was going

Any questions?
duality and conflicting pairs are real, but the statement about worst ever and best ever is not accurate. The issue is that a conflicting pair sets up that possibility with closeness and both people really want to reach it, but something hidden under the surface keeps it from reaching that closeness that you can reach with your dual. So with other relations you wont have that desire to get as close in so many different areas as you do with a conflictor or a dual so you wont get as hurt as you can with a conflicting pair. But life is all about balance and its up to an individual where they want that balance to be. Its not to say that a conflicting pair cant make it, but that you are both gonna have to do some digging both seperately and together to get to the root of things. From my experience it takes a dual to reach this point, I dont know any other way to do this personally without that person you can get close to.
And yes I know I am gonna get people who want to fight me in regards to being close with those types that are with someone other then their conflictor or dual.
Wall of text is done. Sorry, but I got alot of experience with both conflicting and dual pairs and I love to dissect interactions and understand them on all levels. My duals helps me to detach and do this, my conflictor causes me to get stuck in trying to understand the issue that they wont tell me.