Macworld has been doing some more testing in Thunderbolt performance, this time between the Snow Leopard and Lion operating systems. The results say that if you spent that $30 on Lion just so your Thunderbolt connection would go faster, you probably wasted your money. Results weren't that different, coming in only a few megabytes a second apart but still well within the optimum speed for the various transfer services. In general, Thunderbolt's going to be fast no matter what operating system you're using it on.
Macworld also did some testing between the MacBook Air and the 17" MacBook Pro, and again, while the Air's flash memory gave it the edge in a file writing test, most of the speeds didn't differ more than a couple of megabytes.
In other words, there are quite a few other, more important considerations to keep in mind when you're looking for a system, besides just how it runs Thunderbolt. If you're looking for what will really limit or boost your file transfer performance, you'd do better to look elsewhere.