ok what about 2 small SSD vs 1 bigger one?
One bigger one for certain.
1) It will be faster since it will have more nand chips that can be accessed in parallel. Sort of an internal raid-0.
2) A single image is easier to manage.
3) Raid-0 of two small ssd's loses you trim which can be a performance hit.
4) Raid-0 of two small ssd's gives you no noticeable performance benefit. I tried it. two x25-M 80gb ssd's in raid-0 did not seem to perform as well as the single x25-M 160gb drive I replaced them with.