The major difference is writing speed - regular 840 has up to 230 MB/s, vs the Pro which is double, in the 500 MB/s. Hence, people using it as boot only drive say these drives are the same. Besides TLC vs MLC nand, writing speeds are drastically different.
To me, it is OK drive but for around this price there are better alternatives. This is good cheaply made drive that Samsung is asking too much money for...
What is a better model in this price range?