Yes, ssd will be much faster as an OS drive.
Most modern 7200 rpm drives are as fast or faster than these old velociraptors. (there are new versions but they are also much slower than an ssd).
The only part where these 2 in raid0 might be faster is in sequential write speed vs. certain ssd's (like the intel one). But large sequential writes are rare IMHO on OS disks and other ssd's like the crucial one will stil be faster than raid0 raptors.
The advantage of ssd is in random reads and writes where they are magnitudes faster than HDD's. And what does the OS do? "Tons" of random reads and writes. If your computer is stuttering, in most cases it's due to the hdd's.
With ssd your system will be much more responsive and boot and application load times will be much faster.
Downside is of course price per gigabyte that's why it's still rather exotic to have an ssd. I don't know anyone in RL except me.
