As tested by Consomac using the Blackmagic Disk Speed Test, the 2019 MacBook Air can attain read speeds of 1.3 GB/s read and 1 GB/s write performance.
The equivalent 256 GB SSD 2018 MacBook Air could top 2 GB/s read and around 0.9 GB/s write speeds.
Therefore, the new SSD component in use has marginally superior write speeds but 35% slower read speeds, falling from 2 GB/s to 1.3 GB/s. (The 128 GB SSD option has slower 0.5 GB/s write speeds, but this drop-off was also observed in the 128 GB 2018 Air.)
MacDailyNews Take: Win some, lose some…