840 Pro vs. 840 EVO

The 840 Pro uses MLC NAND and is faster, the 840 EVO is newer and uses TLC NAND that has fewer life cycles so theoretically it won't last as long and is a little slower. However in real world use you'll be hard pressed to feel the difference between the two and there was a test that showed the 1000 cycle theoretical limit of the TLC NAND was exceeded by 200%. They managed to write over 3000 cycles before the drive started getting errors. That's the main difference between the two. The TLC NAND in the EVO is why it's inexpensive to make since it's higher memory density. In the long run, they'll both probably outlive how long you'll keep the computer. If you want the best performance go 840 Pro but the unless you do a huge amount of file copies, if you don't need the highest speeds the 840 EVO is already blazing fast.