Guess I’ll decide this as and when
I’m actually gonna play it in 15mm, i e when I’ve got an army. So far we’ve used imperial by default.
The advantage of metric (in gaming) is you get a much bigger "area" to play with, Imperial you get more "realistic" space. Two foot by two foot translates to 1500x1500 with metric.
Not sure how second edition templates translate, as you would need 10mm diameter bases for the figures.