I ran Xbench on both (I own both) and the difference is less than 10%. And I can only tell reading the results, because nothing else I do on either machine reveals to me which is which.
Sequential Write 4k:
277MB/s vs 198MB/s = 39.9% samsung advantage
Sequential Write 256k:
185.22MB/s vs 173.21MB/s = 7% samsung advantage
Sequential Read 4k:
29.50MB/s vs 34.51MB/s = 17% toshiba advantage
Sequential Read 256k:
209.65MB/s vs 210.91MB/s = 0.6% toshiba advantage
Random (same order as above)
84.58 vs 52.51 = 61% samsung advantage
193.31 vs 215.02 = 11% toshiba advantage
12.39 vs 15.59 = 25.8% toshiba advantage
160.80 vs 112.09 = 43% samsung advantage
Unless you're plugging in something to the thunderbolt port that can take advantage of the speed the difference becomes moot, usb and wifi will be the bottleneck and both are slower than what either drive is capable of.
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It's closer to 25% or less in most of the tests I've seen.
http://9to5mac.com/2011/04/16/apple...r-samsung-ssds-for-new-macbook-air-shipments/
The next big leap will come with SATA 3.0 SSDs capable of 6GB/s. I think the ASUS UX21 and UX31 may ship with those drives. Those would be noticeably faster than either the Toshiba or Samsung drives. I've heard that the MacBook Air controller is capable of accepting SATA 3.0, so it's entirely possible we'll see these drives added mid-stream, just as we saw the Samsung drives added mid-stream into the 2010 MacBook Air, and the Toshiba SSD added mid-stream into the 2009 MacBook Air.
I wonder when those drives will come to the Air, probably silent upgrade, hopefully my ssd dies within applecare and after those are the norm XD
In the mean time i'm pretty happy with the performance of the toshiba ssd and the lg screen