it seemed to me that willow was a little more in love with the idea of oz than oz himself, though i think she loved him too. just oz more

I would say that Oz loved Willow a little more than she him. But her reaction to his leaving leads me to believe the love was equal. She took it really hard, so I think they simply expressed the same amount of love in different ways.

agreed^

I think Oz loved her a little more. Like by the end, even though he left he hadn't moved on and he came back to be with her, but she had moved on to Tara.

Oz lovd her more. I agree with spikes_girl that the idea of Oz was important to Willow. Not that she didn't love him but she had been the geeky outcast for so long getting to say "my boyfirend's in the band" was a big deal for her.

And when they both cheated even though Oz went further, it almost seems like what Willow did was a bit less understandable. Oz cheated after Willow already had, so their relationship had already been changed by betrayal, and he was drawn to veruca because of the werewolf thing.
With Willow and Xander it wasn't primal urges it was the fact that she had a crush on him and it was lots of times, you don't have lots of smoochies behind the back of your real love, i mean did she ever cheat on Tara?. Also she cheated when their trust was still in tact.

Bellona, I hear what you're saying about her not cheating on Tara while she cheated on Oz, but I think you also have to factor in the fact that she was a lot more mature when she was with Tara. I mean, she was only in high school when she fooled around with Xander after all, and teenage emotions are not as stable/mature as we would like to think they are when we're that age.
It would be interesting to see what would have happened if she had dated them at the opposite times.