If your data will fit on one SSD that is very much the way to go.
A larger SSD will have more underlying nand chips that can be accessed in parallel to improve sequential performance. Sort of an internal raid-0.
Raid-0 on hard drives does nothing, as a rule for normal desktop operations.
The benefit comes from being able to overlap accesses across two drives, and that pattern is not common unless you are processing large datasets sequentially.
Benchmarks look wonderful, but are misleading.
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.