I firmly believe that Yuuri speaks better English than Viktor.
Like they’re both fluent and speak VERY GOOD English, but Yuuri just got off a five-year stint in a country where English is the predominant language, where he had to speak English every day just to function in society. Viktor’s experience with English is pretty much limited to international competitions and if he forgets a word, it’s whatever, because half the other people there aren’t as fluent as him anyway.
This headcanon doesn’t really matter most of the time bc I write them communicating in English (Which they canonically do, it being their only shared language) so obviously they effectively have the same amount of fluency that I do, but I just love the idea that sometimes, out of no where, Viktor will pause in the middle of conversation and get this look on his face.
“Did you forget the word?” Yuuri will ask kindly.
“What’s the word in Russian?”
“Okay, I’m not familiar with that one. Describe it?”
Viktor beams. “Yes! Turkey!”