One thing that was left out of this article is the fact that the Samsung 840 EVO 1TB uses TLC or triple layer NAND instead of the more common 2 layer MLC used in the Crucial M500 960GB unit which I consider to be the only two drives in their class. While you have a tad more space with the Samsung 840 EVO 1TB and it also is likely faster under most usage scenarios, the TLC has a much shorter rated lifespan than the MLC. Now, I know that most people will never wear out an SSD, much less one this large which has plenty of room for the controller to wear-level the NAND, I do like the security of the 3K NAND used in the M500. Now, I understand that torture tests show the top-shelf TLC picked by Samsung tends to outlast its rated writes by 2-3 times and that most 3K rated NAND does the same so you tend to get more than you pay for in this regard.
I already own a Crucial M500 960GB and am considering another drive in this class. The only ones in this price range are the M500 and the 840 EVO. Another advantage is that both of these use the 7mm form factor which makes them more versatile.
While I feel that both of these are very nice drives, I think it should be noted that only one uses TLC in case certain users require additional PE cycles for heavy uses.