Rev B MBA with SSD.
I own the rev B with SSD, and I am amazed by it daily. The SSD really makes it speedy.
You don't need more than 2 GB of DDR3 RAM. It's running at 1066 MHz which is nice RAM.
Now, the rev B MBA with SSD is expensive. I believe the extra cost will save you money in the long run. I think in the long run, the rev B MBA will more than makeup the price difference between the original refurbished and the rev B new.
Also, the rev B will allow you to plug it into a 24" LED Apple Cinema Display or a 30" Apple Cinema Display. My MBA feels like an instant desktop once I plug in the 24" ACD. It also works nicely like a docking station.
So, my advice if you cannot afford or don't want to spend money on a rev B with SSD, definitely buy the rev B 1.6 with HDD over any original MBA. The xBench results from the rev B MBA show it performs better at 1.6 GHz with HDD than the original MBA performed with 1.8 GHz and SSD.
In the rev B, the SSD will make your MBA boot in 1/3 of the time as a HDD. Also, apps open instantly with SSD. And large files are quick openers with SSD. But, even if the SSD is out of reach or over your budget, the HDD will perform plenty well.
Simply put, the slowest and lowest price rev B MBA outperforms the highest priced original MBA that cost $3099 new less than eight months ago.
Remember to the low end rev B MBA still has same awesome Penryn 6 MB L2 Cache chip at slightly slower 1.6 GHz clock speed. The low end still has Nvidia graphics capable of driving a 30" ACD. The low end MBA still has 2 GB of 1066 MHz RAM. The low end still has beautiful form factor and is super lightweight and ultra portable. Oh and still has SATA drive controller.
And, you may be able to upgrade to SSD in the future if you cannot swing it now. Tough at the moment, but solutions may come out in the future to make it possible.
I love my MBA, and I think it is a wise decision for anyone that wants ultra portability yet speed at the same time.
Good luck with your decision.
Cheers.