First lets make sure we understand things here:
- The first way is setting up a RAID set. Here's a write-up that explains them Standard RAID levels.
- The second way is setting up a Apple Fusion drive which is similar to RAID 0 but smarter when you have a HD and a SSD.
RAID'ing is a very good way to improve access speed and/or reliability, but it comes with a cost depending on which RAID level to go with. RAID 0 is great for speed but it can put your data a risk if one drive fails. RAID 1 offers a fail safe image if one drive fails and it still can offer some speed improvement but not as much as RAID 0.
Frankly, I think its smarter to go with an external drive which is setup with RAID 5 if you really want both the speed and the protection.
Apples Fusion drive won't work here as you have two high speed SSD's so there is no gain. If you had a HD in one drive bay then I would go with it.