I think that Willow assumes greater authenticity in her lovers than she has herself. Though with Tara, she also knows that she somewhat writes on / about her and imbues her with meaning.

Oooh, I love how your brain works. That's lovely and intriguing, I'll have to think that over. (You're of course referencing the body-painting scene in Restless, itself an homage to the movie "The Pillow Book", and one of my favorite images in the entire show.) If I'm understanding your meaning correctly, you're saying that Willow thinks her lovers are more "themselves", more "real"/ authentic and perhaps less complicated and thus more easily "known" (she assumes) than she herself is?

But it's complicated, because Tara is also someone who Willow sees as mysterious and far above her and who intimidates her.

I had to read that twice because the show would seem to imply the opposite - Tara is intimidated by Willow. (Although I think their argument in Tough Love was another "we need this for the plot" moment, because I didn't know where Tara's accusation that Willow was scaring her with her power came from. We don't really see that happening in S5 up to then.)

But there's an aspect to Tara that intrigues me; mainly, the way she actually connects with Buffy on an emotional/spiritual level from Who Are You? (she's the only person to know that Faith isn't Buffy and yet she's never met Buffy, another instance of Buffy's friends failing to "see" her - think the Buffybot in Intervention, and S6 before the reveal in OMWF), through Restless, Joyce's death, Dead Things/OAFA. And clearly that is something Willow is actually jealous of, in Tough Love - just as she was initally jealous of Buffy's relationship with Faith in S3. Willow hates being "out of the loop"; she wants to think herself an "authority". She's also unnerved by Buffy being able to hear Oz's thoughts in Earshot - she's jealous that Buffy has knowledge that she herself doesn't have. And Willow is very much about "knowledge" (knowledge is power), but without maturity or reason to use it wisely. I think there's also an aspect of Willow that's as possessive as Xander when it comes to Buffy.

but I do think that Willow is, by the end of the series, more transgressive than Buffy, in both positive and negative ways -- Buffy is the person I'd term as the better person, but Willow the more dangerous and POSSIBLY the greater symbol of hope; Buffy accepts power that's hers, Willow takes power that isn't initially hers and makes it part of her.

Hmmm. I can see where you're coming from with that - Certainly Willow is the one who says at the end of Chosen "Slayers are awakening, all over", and she seems thrilled by it, by becoming part of something greater than herself. It's what I suppose she has wanted, in a sense, has envied in Buffy and tried to match with magic, and it makes sense that Willow is all about power while Buffy's goal was simply to "get the job done". (The rousing speech in Chosen aside, I doubt it's a course of action Buffy would have taken if it wasn't necessary in her mind. It's certainly not something she sought to do prior to this. And part of it was very personal: "You'll die alone".)

I think seeing Buffy as being somewhere in the (relatively, compared to Riley and Harmony) recent past w.r.t. female power, subconsciously, makes sense.

Not sure I understand, could you elaborate a bit? and btw what is "w.r.t."?