Shoot, cafe, I might have to throw a little wrench in your INFJ/ISFJ comparison!!
I was actually going to say one of the things my INFJ friends and I have in common is that we are externally well put-together, and I'd say there's an element of poise and control in how we present ourselves. My ISFJ coworker is equally put-together, but I'd agree the difference is she's more 'proper', whereas my friends and I are more...poised? I think there's a difference. But otherwise, the ISFJ makes pretty good eye contact and is rather direct and you can tell she's 100% 'there' when she's speaking to you, whereas my friends and I are more apt to not make as good eye contact, and be more 'in our head' as we're talking, and maybe not quite as solidly there, or direct?
This ISFJ told me I come across this way - i.e. poised and controlled, and that I present only part of myself to others, and others probably have no idea half of what I'm about - so I think she views me differently in this way than she views herself. And getting beyond behaviors and just visible stuff, it's in actual interactions and WHAT we talk about, that the differences really start becoming apparent. She is envious of my Ni; she thinks it's a huge strength of mine that I can 'connect the dots' (as she puts it) and come to a conclusion from a myriad of details that she'd never even put together. Whereas she is much more detail-oriented, and more meticulous with more of a tendency to get bogged down with pieces of the whole picture.
I would actually describe her as more warm than me, and I agree w/ you on focusing more on physical needs in terms of nurturing, and being more in touch with schedules, and assisting in more *tangible* ways, whereas I assist in much more intangible, 'help you to help yourself' ways. Perhaps I am more thought-driven in my ways of helping, and she is more action driven?? Maybe?? I'm not sure.
I also wanted to add a thought to my initial post; just that I think with INFJ's, you would be hard-pressed to be able to 'type' one at any one instantaneous moment. It's more something you'd learn over time..patterns emerge over time, or different sides emerge over time. A simple snapshot based on one interaction, or one social engagement, could yield very little, and you could easily just see one part. It's only over time that I can see all of the similarities between my friends and I. And then over the longterm a really big pattern emerges, and that would be the Ni Fe, and basically, we *approach* life and process events pretty much the same. Well, that's what I think.