The key advantage that QLC has over TLC is that with four bits per cell, it increases memory density by 33 percent. That means it can save more data in the same form factor. That also translates to lower costs per unit of capacity.
TLC, on the other hand, can go through a higher number of write and erase cycles, which means it’s more durable and is also faster than QLC. Thus the decision to replace TLC with QLC is not as straightforward as it may seem.