The cheaper, problematic TLC flash in some new iPhones is also a worse performer, benchmarks show

If Apple had gone with multi-level cell (MLC) instead of the cheaper triple-level cell (TLC) flash in some capacious iPhone 6 and 6 Plus models, there might not have been the reported random reboot and freeze problems with those units, but that's not the whole story. 

A Korean publication has put the two types of NAND flash storage used in the new iPhones to the test, and it turns out that MLC flash is also a notably better performer in terms of overall speed and idle usage than its TLC counterpart, as you can see in the charts. Rumors are that Apple will be switching entirely to MLC for the next batches, so future owners can sleep tight, while if your current unit is experiencing the aforementioned issues, Apple is said to be replacing those if the issue proves to be a hardware one.