Them celebrating doesn't necessarily mean that they were able to defeat Ur, it might have just been because Ur disappeared and they were just celebrating because the fight was over. Because if they really had been able to defeat Ur, then that would mean that Wendy was able to oneshot a Demon Gate of Tartaros with an injured leg, Laxus was able to oneshot Hades while severely injured, and Juvia/ Meredy were able to oneshot another Demon Gate of Tartaros and one of the Seven Kin of Purgatory. I know everyone's improved over the past year, but for them to have improved this much is kinda ridiculous.
I agree with you here. I mean, I just re-read the chapters. Chapter 481 displays Gray and Lyon both unharmed. Beginning of chapter 482: Ur casually attacks Gray and sends him flying. She claims that "if an attack like that knocked him down, he's hardly grown up at all". Ok, I get the point of all of you saying Base Gray could beat Ur and he was just "waking Lyon up" but why was Gray so affected by that attack? Couldn't he have just blocked or dodged it? Besides, the chapter already shows a Lyon with plenty of scratches and seemingly tired, which means that, even if he's mentally handicapped, well, their battle offpanel must've been rough for the boys. While Ur has no scratch.
Gray wakes up and becomes rebellious: "this is not the kids we used to be". He gets a bit serious and finally gets to lay a scratch on Ur's face. They receive 10x her damage though. Unlike many of you, I think this is Gray getting serious, as he "won't let her sully Ur's name any more than she already has". He's kinda angry now.
Chapter 483 now. The battle reaches its climax. Ur is utterly unharmed and fresh as a rose; the two boys are both tired and damaged. The teacher's attack, Ice Volcano, far outclasses the student's, Ice Geyser. They both get overwhelmed by the spell and in the end are breathing heavily: they're clearly having a hard time. Is this Gray just barely trying? Is this Gray attempting at waking Lyon up? Maybe. But that doesn't necessarily imply he needs to receive so much damage. He's just receiving damage because Ur's power overwhelms him. Besides, he's not just on the deffensive, he's also attacking.
When Lyon claims that Ur is simply too strong for them, Gray tells him that "that's not Ur". He doesn't tell him "this thing is not even close to the power of Ur" or "yes, we've grown up and we've surpassed Ur", he simply states "that's not Ur". Which has no implications on whether the Historia is less or more powerful than Ur, or whether they're more powerful than Ur, he simply says that that thing's not Ur.
Ur is confident that the two of them are no match for her. She clearly states so and she bases it on the fact they're heavily injured whereas she's received no harm and seems to conserve plenty of MP and durability. At the end of the chapter, the two of them land a solid hit on her, combining their powers. It would be advisable to mention that
this was DeS Gray, since the attack is named "Ice Devil's Zeroth Long Sword".
Whether the attack has defeated Ur is up to interpretation. We don't see what happens offpanel, we move from that attack to a point where Ur has already disappeared. I lean on those who claim she was not defeated. There will be those who think that blow knocked her down.
What is very clear in my mind is that Ur outclasses base Gray. Not by far, but she does.