Difference between two SSDs

Hey there, TheCoreyHall.
I'm sure you're well aware of both SSDs' specs, so I can offer you this link: http://ssd.userbenchmark.com/Compare/Samsung-850-Evo-500GB-vs-Samsung-840-Evo-500GB/m19728vsm1519, which compares the benchmark results of the to SSDs. This will give you a bit more info on their performance so that you can make an informed decision when you decide to get one.

Hope that helps. :)
Boogieman_WD