wow, Micron do 70% of embedded over provisioing? and Intel S3700 do 32% too
Normally it is pretty easy to decode the capacity of MLC NAND, but Micron is using NAND unique to the P400m. Instead of the normal 32 or 64Gbit per die, we found NAND with a capacity of 42Gbit per die. With 4 die per package and 16 packages, our 200GB sample had 336GiB of NAND. That comes out to nearly 70% over-provisioning. If that sounds like a lot, it’s because it is. Take a look at our Intel SSD DC S3700 review, the 200GB version had roughly 32% over-provisioning, less than half of the P400m.
So Samsung does ZERO%? maybe this explains why its price is always reasonable?
It all depends on your usage, how many GBs of writes do you see on an average day? I've always used 20% OP with Samsung since the 830s, I would expect the EVO to last less than the Pro, but for normal usage they should still last a long while. As it was discussed in a different thread, the write endurance for the evo 1TB is 63 years writing 50GB/day.
So I wouldn't be too worried about the endurance of TLC vs MLC, unless you specifically write a lot of data. TRIM, however, is important on either as it helps keep write speed at the top of its game.
200GB (out of 336GB) visible to OS equals to ~35% over-provisioning, not 70%!
I think you're calculating this wrong. It isn't that 70% of the storage on the drive is available to the OS, which as you said isn't the case, it's that the drive offers an extra 70% of space on top of the rated capacity.
136GB on top of the 200GB stated capacity (336-200)
136/200 = 0.68
It's not exactly 70% over provisioning, but it's pretty dang close.
I don;t really worry about write endurance nowadays though
what about Samsung 840 "PRO" and Intel "3500" (not 3700), better to do 20% of OP too?
What is your usage? Noone can tell you for certain, you need to look at the volume of writes to determine what an appropriate OP would be. If you mostly just do reads, then there really isn't much purpose to OP on those. If you write a lot, then you may want to have a higher OP.