It's so frustrating the way AI argumentation goes. People will cherry pick outrageously specific items and extend to crazy generalization. I mean... your phrasing was 100% ambiguous! There's no such thing as a "Stockholm bus", or "Stockholm rolling stock".

There are buses in Stockholm, and buses in Thessoloniki, and buses manufactured in Sweden, and buses previously used in Stockholm that are now in operation in Thessoloniki. And one LLM took one path through the question, answering it correctly and completely. And the other took a different one[1]. As it happened your (poorly phrased) intended question was answered by one and not the other.

If I ask the same question with a more careful phrasing that (I think!) matches what you wanted to know: "Where did buses used in Thessoloniki come from originally?"

...I get correct and clear answers from both. But the Google result also has the Wikipedia page for the transit operator and its own web page immediately to the right.

Again, cherry picking notwithstanding I think in general the integrated experience of "I need an AI to help me with this problem" works much better at google.com, it just does.

[1] It's worth pointing out that the result actually told you that your question didn't make sense, and why. I suspect you think this was a bug since the other LLM guessed instead, but it smells like a feature to me.