Just FYI the 512 has faster read/write speeds than the 240. They are NOT the same. I have the 512 and it actually benchmarks higher than Samsung's advertised specs. I am have my reservation about 2 cards, or raiding two 240s for two differnt reasons. I am not sure if all MOBO are the same but loading up a raid driver may actually increase boot time. Thats reason 1. Reason two is these M.2 cards take up PCI lanes. For MOST people this will not be a problem. One slot will eat up one SATA Express lane (or 3 Sata 6b lanes) and the other M.2 will eat up 4 of your PCI lanes. Most people will never need all your PCI lanes, but some may want to. Anyway I totally splurged on this product and I 100% do NOT regret it. Its so fast it isnt funny.
If someone like me does not have an M.2 slot on their motherboard, but has a setup like mine that does not need updating (Work Station) then a PCI-E card with similar IOPs and up to 2 TB storage is a viable option. Intel also offers an Enterprise level in the DC P3500 Series.
Most aftermarket Server Motherboards like Supermicro do not have M.2 slots on their newer boards either.
Three of the four options are the same product, except on is priced significantly lower then the other two. Yet the cheapest of the three is not top voted? I'm not sure if I'm missing something or if it's labeled incorrectly.
of course it price dependent between 512 and 240 , but it would be better and faster if 2 240 SSDs installed in Raid formation using PCI express card (6GB\s total)