You're better off running separate drives, for a couple of major reasons:
1) 50% less data lost in the case of a single hard drive crash.
2) Install the OS and hard drive intensive apps and games on one and put the swap and low intensity stuff on the other. This will help a lot in high I/O situations.

RAID-0 has really only a single advantage, and that's in highly linear I/O such as video editing or transferring massive files.