I don't really get how you can have a stated diameter on braid at all. It just flattens like a pancake when pressed by a micrometer. I have used standard Power pro, but not since super 8 slik came out, which is a far better product. The standard is good but starts to break down, ie it becomes furry. Braid users will know what I mean and this does tend to weaken it. I think this happens when microscopic particles get into the braid strands from the cloudy river water. Or maybe its just wear and tear etc. Super 8 is great, it seems to have a "Slik " coating on it that really keeps the furring down to a minimum and helps maintain the knot strength on the all important leader knot. Super 8 slik is thicker than standard Pp, when compared side by side. The one I have been using though for the last 3 or 4 years is Daiwa J Braid 8, it has a good compromise between Pp and super 8 and comes in more appropriate colours etc, which doesn't really matter tbh, when using a leader.
Trent style I would use super 8 in 30lb for the Trent for heavier fishing but in Daiwa J braid 8, I'd lean towards the 40lb, as it seems thinner and more robust in this BS.