Whatever the majority of the people in the area are speaking. Another factor is which side of the border the community interacts with more. If say the city is technically closer to an urban area on the bordering country than it’s neighbor within its own country, then they likely interact more with the former so will speak that language more.
Boxer briefs are the best of both worlds. Not too tight like a regular brief underwear, not too loose like boxer shorts, and still has adequate ball support.