on paper the raid is much better but what about the downsides? what exactly is RAID and how can I se it up
The term RAID refers to using multiple hard drives in various configurations to function together. The typical method referred to on "enthusiast" sites is the RAID 0 which combines to devices to make them appear as a single device. This allows them to add their capacity together and at the same time allow for higher throughput numbers in reads and writes.
While a RAID 0 looks impressive on paper and in benchmarks it is markedly much less so in reality and day to day use, especially with SSDs. You see the RAID 0 is truly master when it comes to massive sequential file use, using a single large file only. However the reality of computer us is that in day to day usage this does not take place. Using Windows or even 99% of programs is not about opening a single large files but literally hundreds of portions of smaller files. Because of this the throughput pipeline of the HD cannot become filled and the speed offered by the RAID 0 lays dormant.
The speed advantage of SSDs however rely on the seek times, which are near instantaneous. You see the slow down of the traditional HD in daily use is the time between finding each of those small file pieces and then moving to the next. With the SSD being so much faster at doing this you get the resulting snappiness that the SSD provides the computing experience, this is not helped in a RAID.
Additionally as pointed out a RAID 0 carries a risk and the risk is that if one of the HDs fails the entire system fails. Now on the surface that sounds like a DUH moment, after all if a single HD fails in a single drive system the computer fails. What makes the RAID 0 worse at this is simple laws of average. You see of you have two drives the chance of one failing is actually increased. Not dramatically mind you but there is an increase. So in essence you are increasing the chance of system failure by a small percentage for performance boost that benefits nothing but benchmarks.
Now based on the prices you presented I see the benefit of the two smaller drives but I would not set them up in a RAID. I would set up one as an OS and business app drive and the second for my STEAM account and other games if you are a gamer.