I'd get the 840 EVO, followed by the M500 if you want something a little cheaper/slower. Everything faster and your just throwing away money for no real gains IMO. You will not notice the difference between a 840 EVO and a 840 PRO... plus the EVO comes in 1TB form!
A 1TB EVO with 50GB/day writes will last ~23,000 days. Even if you do 250GB/day writes, it will last over a decade. By then we'll have bigger and faster SSDs for far cheaper. Spending more for better durability is only needed for enterprise level servers that are doing constant 24/7 very heavy loads.
I was looking for a good choice between value/performance/durability and I found it thanks to this very clear answer.....EVO here I come