Some new MacBook Airs are performing slower than others because Apple is using different SSD suppliers for the notebook, according to TLD Today.
Engadget reports that "Jonathan over at TLD discovered a fairly significant discrepancy when benchmarking both MacBook Air models over the weekend. The 128GB Samsung SSD in his 11-inch Air was able to achieve 246 MB/s write and 264 MB/s read speeds. When he switched to the 13-inch model, however, speeds dropped to 156 MB/s and 208 MB/s, respectively, using that notebook's 128GB Toshiba SSD."
We reported on the new Samsung SSDs back in April. It's surprising to see that Apple has decided to ship both the Samsung and Toshiba SSDs simultaneously which is a bit unfair to unlucky customers.