Consumer SSDs use MLC. Enterprise SSDs use SLC almost exclusively or eMLC which has less issues than consumer grade MLC.
MLC is about storing multiple bits in a single tiny cell. This results in more capacity at the cost of total write cycles, read errors being more likely and slower read and write speeds.
TLC is MLC but with three bits per cell.
The 850s use 3D NAND at 40nm process, and in terms of performance and capacity per dollar are pretty much still unmatched.
I haven't kept up with that, I'm still using Samsung 470, 830 and Crucial M4 SSDs, which are rock f&^king solid, knock on wood.
But when they were released, with their much lower price tag, their TLC chips (with a huge SLC buffer to make it seem faster) seemed a bit suspicious - basically cheaper MLC, and that's not a good thing in this case.
Remember that? It affected all Samsung EVO drives, which is marketing speak for all Samsung SLC based drives, which means budget drives, the Pro versions based on MLC were unaffected.
But, the way Samsung handled my case, to deny warranty, and in general case to release an .exe file on their website called "Slow fix something.exe", has me stay away from Samsung SSDs for ever.
The other "fix" they had was to release a firmware which would shuffle data around in the background - reading and rewriting/updating cells - so as to appear that there is no problem - but read speed would anyway decrease with age, and increase the write-cycles on the cells even if the SSD is idle... Fun.
I recommend SanDisk Extreme Pro -- they are awesome good value drives - may exist newer on the market now, but last autumn those were and still are the best SSDs ever.