So, which way do you say it? And which region says what?
I assumed Mainland China said it 披頭四 and Taiwan said it 披头士? But I'm watching this video about Paul McCartney https://www.youtube.com/watch?v=E7Vx2ogiJ9w, and she says it 披头士? But she looks Taiwanese?
Maybe I'm wrong!
A quick way to do this is to use Wikipedia's localization for Chinese:
If you want to widen the search a little:
The person in the video you provided does not sound like she is from Taiwan. She also employs the term 披头士 - which according to the above wouldn't be very "Taiwanese."
The YouTuber does use traditional characters in her video titles. This, assumedly, is probably what spurred your presumptions. The reason for writing the titles in this way is most likely due to the fact that YouTube is blocked in the mainland and the majority of Chinese speaking YouTube users are from Taiwan or other regions that use traditional characters as opposed to simplified characters.
Another cool tool:
LiVac has some really interesting demographic spread data. For instance lets look at 披头士:
Lots of hits in the mainland, nothing in HK or TW. Some minimal hits in Malaysia and SG.
Conversely we can look at regional information for 披頭四:
We can see quite the contrast. Zero hits on the mainland, but with big hits in HK + TW. And again, some minimal hits in Malaysia and SG.
In "Taiwan Panorama" articles, it's almost invariably written as 披頭四. E.g. 搖滾樂自1950年代中期誕生至今，歷經披頭四、滾石等樂團的經典熱潮，而後繁花枝葉盛開，揉合出多種類型；... "Rock music was born in the mid-1950s, growing through bands like The Beatles and the Rolling Stones and blossoming from there into a variety of subgenres."
披头士 is the official translation in mainland. The translation of "s" to "士" is a style of translation in Taiwan which I think follows Canton Chinese (South Chinese dialect has no retroflex) which originated from early contact of China with the West. Taiwanese and Hong Kong Chinese can keep this style due to the civil war of China and the fact that the elites of China were mostly south Chinese before 1949. Mainland does not have this style of translation, except few old historic translation restored due to tradition like from "迪斯尼" to "迪士尼".
披头四 is a more vulgar and disrespectful translation. I did not see it used in mainland China. Beatles was not introduced into mainland China for the purpose of criticism of the West (when the mainstream atmosphere in China was adoring the West because China was so underdeveloped at that time), but as a sign of prosperity of the West and of western ideology, so China should not have used 披头四 as the translation.
It is a transliteration, which is very common when introducing foreign words to Chinese.
披头士 in Chinese pronounces very similar to Beetles in English.
Other examples, 沙发 - Sofa, 咖啡 - Coffee, 粉丝 - fans, 酷 - cool，迪斯科 - disco， 比基尼 - bikini， 卡司 - cast， 克隆 - clone， 朋克 - punk， 唐宁街 - Downing street，巴士 - bus，妈咪 - mummy， etc.
