T’is a valid question about the difference between porous friction course (aka open grade, popcorn etc) and grooving. The short answer is that, for performance engineers and pilots alike, there is no difference at all.
The long answer would run to hundreds of pages, and would come to exactly the same endpoint as the short answer.
For those students of human frailties, you’ll be amused that the choice of friction treatment is little more than the “flavour of the month”. Today, for example, Australia is in the grip of the ‘grooving school’. The British seem to be slightly more in favour of grooving – perhaps it’s all those regimented ‘stripes’ that attract their attention. The South Africans don’t trust grooving at all – since it must have been a remnant of a previous dispensation. The Americans like both; varying between grooving (for the groovy) and porous (for popcorn lovers). The Germans like SMA, because they invented it. The French like anything that is spelt in French.
For myself, I have given up on making a choice between the two. Whatever the airport wants is fine. They both work as well as each other, and there is no point trying to persuade a dedicated stripes man that he should choose something full of holes, and vice versa. All I want to see is that the airport has one of the friction treatments.