The overall consensus from the hardware sites is that this 840 non-pro overall is *slower* than the 830. If you can find the 830 for the same or less, go with it. 840 Pro obviously would be better choice but is currently too expensive to some.
The 840 is SLOWER than the 830. The 840 PRO is FASTER than the 830.
Basically: 840 PRO >> 830 >>>>>>> 840
We deploy a lot of SSDs for servers and cloud hosting, and the 830 is a fantastic drive, and the 840 pro is even better. The 840, however, uses TLC NAND, and because of that is far far slower. We will be completely skipping the 840 for our customers and only going 830 and 840 PRO.
Your summary is a bit disingenuous. The 840 is slower sustained read/write (e.g. when you boot/shutdown) but random read/write of 4k blocks it is superior (your typical work with a computer is much more like this.)
Let's be honest, most people aren't working with gigs of data at once.
My understanding was that TLC was slower for random read/writes than MLC. Also because it has 3 bits per cell it degrades quicker than MLC, leading to shorter life spans.