Well for starters this question should have been asked in the storage section of the forums. Second, we need to know the answers to a few questions:
How much money is in the budget?
How much space do i really need?
Will this be a boot drive also or just a storage drive?
Can I do the basic maintenance to keep an SSD in tip top shape?
Do i really want raid 0? (have you looked at other options?)
In terms of pure speed I would say the following list is a general estimate:
1. 2xSSD in raid 0
2. 1xSSD or 2xHDD in raid 0
3. 2xSSD in raid 1
3. 2xHDD in raid 0+1 or 3xHDD in raid 5.
4. ?xHDD non-raid or raid 1.
Keep in mind that when running pure raid 0 or using a single drive any hard drive failure will end in a complete loss of data. Also consider that normal HDD drives offer much more space for the money. compare 1.5tb (HDD) with around 60gb (SSD). If you have to store any large amount of information costs can get excessive.
Some users have been known to use an SSD as a boot drive, and for some programs but use HDDs for storage. Personally I use 2xHDD in raid 1 and I have no complaints about access times.
Hard to say without looking up actual benchmark numbers. I think for most lower speed SSDs raid 0 is faster...and with some new high-speed models raid 0 is on par or slower.........dont quote me on this.
having a SSD as a boot drive works fine for alot of people. Keep in mind that some older motherboards/bios do not recognize the drive at first and require flashing. Do a search on google for "use ssd as boot drive" and you might find a few good articles on this topic. Other than this i wouldnt say they are any worse than having a HDD as a boot drive....my one hdd failed after only 6months! then its replacement after 1month! so you cant say SSD<HDD in terms of quality
Tomshardware probably has HDD/SSD speed benchmarks if you look for them. raid 0 is around 1.6-1.8x single drive speed (wont be full 2.0 b/c of raid controller processing)