At current prices i can't see why would you put 2 SSD's in a RAID 1 config in a home situ.
What i do is use a NAS drive (I have netgear duo and synology) with RAID 1 for data on normal disk. This means the data is available from my PS3's, TV's, Phone, Laptop and Desktop and even over the web at all times.
On my desktop and laptop i put my OS (win 7) is on a 60/64Gb SSD system disk (at a cost of £50) If the disk fails. I'll just replace in the future. £50 will buy a much larger disk next year or hopefully in 5 years time and I won't have lost any data.
I am pretty sure in most home situ's an SSD disk will have the highest WEI score, and the processor, graphics chip etc will be the bottle neck.
I realise if you're running super high end games machines or need performance in an enterprise environment you will have different needs. But £50 system SSD disk (eg OCZ Vertex 4 64GB) is all you really need to get the benefits.