SSD is always faster. Raid ssd is fast but don't have TRIM. However, TRIM is a window 7 and vista function only, so if you use window xp, raid ssd is makes no difference (I am uncertain about linux or fruit brand os, I think linux ike ubuntu have them and fruit don't? people with more knowledge on those os please correct me if I am wrong).
I would suggest 1 fast ssd (as fast as you can get) and raid HDD (as many you can get in your budget).