Both- I was brought up in kilos and gramms, but then lived all my adult life living in UK using pounds and oz. I have books in French in kilos and gramms, and others in English, some in lbs and oz, some in kilos, and some in both. I have old fashioned scales, brass pan on cast iron body, and 2 sets of weights, round ones for pounds, etc, octogonal ones for kilos, etc.
One of my favourite baking book is still my vintage Be'Ro flour book, in lbs and oz only, but I also have a later one with both 
Like using two languages daily, and driving both on right and left side, two 'cultures' etc- it keeps the mind active 