Spurs are again in Premier League title contention, sitting second and seven points behind Chelsea, while City have slipped to fifth.
But the Argentine feels their meetings in England are different, with Tottenham – who last won a league title in 1961 – the bigger club.
"[In Spain] the gap was massive, massive. Now, historically Tottenham is bigger than Manchester City. The fans are bigger at Tottenham," Pochettino said.
"You can compare in Spain. Between Espanyol and Barcelona, you can measure the gap. Here, it's too difficult to measure the gap. It's a completely different world."
Guardiola has faced criticism to begin life in England, and City were thrashed 4-0 by Everton last time out.
But Pochettino said the former Barcelona and Bayern Munich coach had nothing to prove, given his previous successes.
"It means nothing for City to lose to Everton. It does not change my admiration or my thoughts about him. Sometimes you can win, you can lose. That is the game," he said.
"He needs time. He's in a position that is still that they can win titles. And he only has to wait.
"He doesn't need to show his quality, his real quality as a coach and how he manages the team. He's shown enough at Barcelona and Bayern Munich.
"Sometimes it's about managing expectations. You cannot win titles after a few months. You need to wait until the end. And I'm sure Guardiola will fight with Manchester City at the end for big things."