I guess I would be the one to dissagree here. I think it would be a close fight, providing that the fight took place in Buffy's demension and not in Glory's, otherwise Glory would crush her in a matter of seconds.
Now this would be why I think Glory would win. First off, we saw that after Glory brain-drained Tara, Willow was pissed. For all Willow knew, there was no way to reverse the affects. So when she went after Glory we saw about.. I would say a good 70-80% of what Willow was capable of as a witch. And remember, that Willow ran out of power VERY quickly in her fight against Glory. Which afterwords, Glory brushed off like it was nothing. Sure, it hurt her real bad but she recovered from it at a very rapid pace. Her second two spells didn't even have an effect on Glory.
and even after Willow finished her assault on Glory, Buffy came in and glory was still strong enough to take the both of them on at once. I think that if Glory had any idea that Willow's attack would have been so powerfull she wouldn't have gave her the chance to use her attack.
and even if Willow powered, physically, to fight Glory, like she did Buffy, Glory would still win. Why? Well let's take a look at what we saw between the fight between Willow and Buffy then the fights between Glory and Buffy, Buffy was able to stand up for herself when fighting Willow, not so much with Glory. And during all the fights with Buffy, Glory was just messing around with her, she never really went at her with everything she had. The only time she arguably did, was in "The Gift", but Glory was brain-drained by Willow leaving her at an extremely unfocused state, which greatly hindered her fighting ability. Not to mention by the time Glory was getting serious, Buffy had already hit her a good couple of times with that troll GODS hammer/wrecking ball.