fartwhat? /j
Definitely Fahrenheit, I'm just out here fighting American centricity on the internet by being annoying and pedantic. The USA is the only country, besides some islands and territories, to use Fahrenheit for outdoor temperature, the rest of us moved on to more civil units of measurement.
Equally peeves me that people often say "Canada" (no, Canada is big, it was Manitoba) or "Europe" (you can say "Portugal", we actually did learn geography). But "Arizona"? Go right ahead, of course we should all know US states by heart, because the USA is the centre of the world!
I've been thinking about your comment lately, you're correct that Arizona is physically larger, but Portugal has a larger population, so they should still be on equal footing.
Regarding Fahrenheit... I'm sorry, I can't see it. Living in Canada, all I care about are two things: when is my tea ready, and when is it going to freeze outside. I can give up having a round number for a fever (37.7°C, which we know by heart as also being the threshold for "hot" in air or liquid temperature) and for a... mixture of ice, ammonium chloride and salt at 0°F? Today I learned.
Bref, I still don't see the purpose of Fahrenheit for my life since it's really important for us Canadians to know the freezing point of water so we can bring in things that are frost sensitive, and it's an excellent point of reference to be able to tell how far on and on which side of the freezing scale a specific temperature may be. Maybe if you lived in Arizona, Fahrenheit may be more useful?