I felt some speed increase when put my cards in raid 0, I would defiantly have my boot drive in raid 0 if that's an option.
Some may disagree and say that the extra risk is not worth the speed increase.
Try for your self if you wont notice any difference you can go back to a single lower risk setup.
You may want to take into account that if the cards are old the risk of a drive failing is more.
If you make sure all your important files are one the other drive the risk is the same in my opinion so i would recommend raid 0.