Socionics' hypothesis is that relations are best within one's own quadra.
I find it to be true, in my own experience.
Lately however, as I've begun to understand more about subtypes... I realize that intertype relations, even w/in quadra, can have varying degrees of comfort.
For example: almost ALL of my best friends are producing subtype betas... My best friends are fe-infp and se-istj... (my older bro, ti-estp, is one of my best friends as well.) These ppl seem to understand me clearly, without any strain on either of our parts.
I have more strained relationships with se-estps and ni-infps... (not so much with the accepting subtype of my dual, ti-istj.)
Can anyone else speak to this..?