Hmm I won't call neither of the teams having a giant history but most likely a good recent history but so far City did not won a single international trophy so maybe it's time for that 2012 final when Chelsea had pure luck and a Drogba in monster mood to rotate around City and take the win and the tittle. Also Guardiola really lost ages from his life trying to win the UCL again with both Bayern and now with City so maybe it's time for him as Tuchel proved that he is a future coach that probably will win his title at some point , maybe even now but like I said the odds are with City and Pep.
They can be called as big teams in Premier League and giants in the last two decades. They are not deserved to be called as giants in England if consider all history of that national league, before and during the era of Premier League.
In Champions League, they are not giants. Chelsea have only one title, long time ago and this is the first final match for Manchester City.
With the changes from Pep, reduction of perfection obsession, and less weird choices for his squad in important matches, I think Manchester City can win the final match. They dominated the Premier League and can bring it to the final match. Nevertheless, football is not predictable and it is a beauty of it. Chelsea have their chance to win, even it is small, but they can.