News Apple Mulls Using 3D NAND from Chinese Supplier YMTC

how do you validate the quality/performance between devices with different parts?
You define a test that the device must pass, of course.

For example, "the device must achieve a specific score by running a specific benchmark for some specified number of hours before running out of battery at a specified ambient temperature"

It's really not that hard, and devices with different parts have been around since forever. Even gaming consoles can have different parts (usually the disk drive).
 
Is YMTC still stacking NAND cells on CMOS combining 2 different wafers or have they finally got a CMOS under array on a single wafer part of their process? If they are doing the prior still not sure how they can be cost competitive.
Its TLC cells so 600-2000 cycles, if the reliability is there and it is the cheapest, makes sense from an Apple margin point of view. Its a small market (Hynix, Samsung, Kioxia, Micron and these new up & comers).

From what I can see on alibaba looks like the cells are only rated for 600 cycles, so at the minimum for a TLC. At $150 I think I would rather pick up SN850, but apple surely has a volume contract and likely there own controller and integration putting the price in favorable light to make the switch and qualify it up.