What your T said about not being able to accept the things he doesn't know..... Holy cow! I never thought of that one! And, I can see the truth to it. Of course, he also can't reject the things he doesn't know, which is the point in not telling people stuff. And, theoretically, we're supposed to be learning to trust people... The only way to do that is take a chance...
I don't have an opinion on who you should go with. You're there. You've met them. I would trust your instincts, so I think you should trust them too. And, you can change T's at any point down the road, right? This isn't a deal where you have to do it now or never?
On the "borderline" thing.... I don't know. I took one of those online tests once and came out "borderline borderline", But, a lot of those traits can be explained in other ways. What my T says about labels (and I really like this) is that none of these "diagnosis" are really discrete, precise things. You don't exactly "have" PTSD or BPD in the same sense that you "have" blue eyes. He says there are ranges of characteristics that everyone has more or less of. When you have enough of these characteristics that it becomes a problem for you, it's a problem. When you have enough of these characteristics, it also pushes you over a rather arbitrary line that exists more for paperwork purposes than anything else, and you get an official label.
Take "no sense of self" for example. I guess that goes with BPD, but wouldn't you expect something like that from anyone who never got the chance to learn that they were "important" as themselves, as a child? Who never got to learn to HAVE their own identity?
Personally, if I were you, I think maybe at the next session with T #1, I'd throw the "borderline" idea out there and see what he says.
From what I've read, I fit a lot of the criteria for schizoid personality disorder. (Another real winner, because they basically say it doesn't respond to treatment, and there's some debate about whether or not people who have it even view it as a problem.) I've thought about asking my T. Decided not to. He either thinks it or he doesn't. If he thinks it and doesn't want to give up, I'm good with it. (And he's been pretty up front about the fact that he enjoys a challenge as long as the "challenge" is willing to try, so who knows?) If he thinks it and doesn't want to freak me out by telling me..... I guess I'll assume he knows what he's doing. If, at some point, he brings it up, I'm good with it. In my situation, I'm not really trying to make any decisions about him, though, so it's different.
I'd be willing to bet, if you ask him the question, he'll say he doesn't think so and give reasons why not. See if the reasons make sense to you. (?)
I'm not an expert. There are lots of people here who know WAY more about trauma therapy than I do. I DO think you need to work on trust in this process. I'm skeptical about JUST working on that by tackling "the hard stuff". I think you build trust with a series of small victories and insights. There may be big ones too, along the way, but one big thing after another sounds pretty rough. But, you can actually talk to him about THAT too. You may as well thoroughly talk through it and see what he says. The worst he can do is "fire you" and then your decision is made!