I don't think anyone knows exactly how long the TLC V-NAND will last, so if you want some more proven longevity, I would go with the MX200 as MLC is generally pretty durable. The MX200 iirc is Crucial's higher end set anyway in the consumer market. I would pick it over the 850 Evo any day.
I've stated this multiple times but after what happened with the last set of Samsung's new experimental tech, I would not in any case go for something that isn't based on tech that has been out for several years.
I got one of the 500gb evos over the black friday/cyber monday week, and yikes that shit is fast. Windows 7 actually loaded in about the same amount of time as it took my monitor to detect that a signal was being sent to it. My old Kingston V(something) in my other computer wasn't anywhere near this fast.
Of course with all the updates applied I do expect it to slow slightly, but still it's a nice gauge for speed.