Because I take my Eee PC 901 always with me, I'm pretty sure it will be broken in less than two years. The last Subnotebook I had had was broken because it fell down a stairway. That's when I decided I will never carry a 1k € notebook with me anymore, and use a Netbook in the future.
Knowing that, I wanted to store my user profile on a disk that I can easily detach from the EEE when it's broken. The C:\ SSD is build-in so no chance to detach is. Only solution left: Either the D:\ drive (the 12 GB SSD) or a Secure Digital card. Because I have a lot of different SD cards around here, I have done some performance test with CrystalDiskMark. The list below shows the results, sorted by Random Write 4 KB (bigger values are better).
I now have my user profile on a Kingston Ultimate 133x disk and so far everything works fine.