Hi.. Yes I've researched the forums.. but I still need some clarity on this. I just had a 4GB, 256GB refurbed i5 13" air. The SSD seems incredibly fast. I returned it due to the 4 GB. In its place I've got a i5, 8GB, 128GB 13". The SSD on this one seems much slower. When I run the Blackmagic speed test, I'm getting write speeds of 200+ MB and read speeds of 650+. On the 256 both speeds were upwards of 700MB. Is it fair to say that the 256GB is more than twice as fast as the 128GB? Does the 512GB get much faster than the 256? thanks.