I find it difficult sometimes, the way knitting needles are not universally sized, and some patterns mention a needle size without stating US, or Metric. We usually have to do a bit of detective work to understand fully, check the gauge, or research the yarn. I pride myself with being bilingual in knitting needle sizes, only looking up the more obscure 13US/9mm, and only have a tough time with the elusive 7mm = ???? Being Canadian, I tend to "get" the metric numbers, as they relate to the ACTUAL diameter of the sticks. I am also quite Bilingual with the 50gm / 2oz skeins, and can convert Kg to Pounds and back. Handy when ordering full cones of lace weight and knowing if it's enough for a wrap or full size triangle shawl. I can do the length of sleeve in centimetres or inches. And I understand that 25 Celsius and 80 Fahrenheit are pretty much a nice sunny summer day. I also can make my car go 100 KPH or 60 MPH, and know when it's OK to do more than that (most of the time).
So, if there was an official vote, I would make all the needles metric, and balls of yarn grams, and length of sleeves centemetres.... and I definately like driving 100 kph, as it sounds way faster than 60 mph.
Works in Progress: Here's the stainless steel scarf so far....
You would think being Canadian would also have me bilingual in French and English, but other than recognising the french side of the cereal box and turning it around, not so much.