Yeah I really like my 840 pros, man.
The 850 evo and 840 pro are very similar. I think in realistic situations, you wouldn't be able to tell any difference between them. However the 850 evo does pull ahead slightly in benchmarks so more than likely would be the better choice for most situations, I think it's also cheaper now since it's easier to get a hold of than an 840 pro.
I highly recommend Samsung for SSDs in general. Love them. I think you can't go wrong with an 850 EVO.
The 850 evo and 840 pro are very similar. I think in realistic situations, you wouldn't be able to tell any difference between them. However the 850 evo does pull ahead slightly in benchmarks so more than likely would be the better choice for most situations, I think it's also cheaper now since it's easier to get a hold of than an 840 pro.
I highly recommend Samsung for SSDs in general. Love them. I think you can't go wrong with an 850 EVO.