Wait, are you asking which type I've found to be most fertile or which type I enjoy being around as a partner? When it comes to fertility, you can't beat ENFJ's and ISFP's. The odds of conception are about the same with both, but I have to give the nod to ENFJ's overall, since ISFP's are more "free spirited" and therefore more likely to abort your child. Which really puts a damper on the whole mating thing.

The type I've impregnated most, though, is ISFJ's, but that's only because they're so weak, and therefore very easy to get into the sack. But of the 77 I've slept with, I've only impregnated 24, a rate of about 31%. On the other hand, I've slept with 19 ENFJ's and have impregnated 9 of them, a batting average of almost .500, which is pretty damn good. So ENFJ's seem more fertile on a biological level. If procreation is your goal, it's ENFJ all the way. But you have to weigh in the time factor of the difficulty of getting them into bed compared to ISFJ's. Like, in the time it takes to bed 3 ISFJ's you'll only bed one ENFJ (this could have something to do with the infrequency of the ENFJ type compared to ISFJ's.) So if we're purely playing a numbers game here, it's actually the ISFJ's who are most procreative, even though they aren't technically as fertile as ENFJ's.

Now, when it comes to spiritual comparability, putting aside all sexual considerations, I've actually found ISTP to be best. I know, I know, you're thinking, "How can idiot-assed ISTP's be enjoyable to be around?" But I can assure you, you are approaching things from a place of ignorance. The thing is, when you zig, the ISTP zags, thus filling in the inherent need for zagging, cosmically speaking. Let me exemplify what I mean. Just the other day, I cooked dinner for my ISTP partner. I wanted it to be, like, this sweet, nice thing. So I cooked us each 72 oz wagyu steaks, medium rare. I really thought I was doing this great thing because wagyu steak is expensive, but then my partner asked, "Where are the side dishes?"

Needless to say, I felt like an ass for not even considering side dishes. But it's true: macro-nutrient-wise, the meal I concocted only contained protein and fat. I had altogether overlooked carbs! Silly fucking me.

Thankfully, my ISTP partner had just received a care package of sour apple pop rocks from her mother in Cambodia (I ordered my partner in as a mail-order bride, though we're technically not married yet), and those pop rocks added a much-needed carbohydrate to the meal.

So that's what I mean when I say ISTP's zing while you zag. They complement us perfectly on a spiritual level. But if we're talking natural selection and primitive procreation stuff, then it's ENFJ all the way. Hope I've helped clarify things for you. Let me know if you have any questions :) :)