Apple's iPhone 18 Pro Max uses QLC NAND to offer more storage, but testing from Homolab, reported by Tom's Hardware, reveals a performance trade-off under sustained writes. During heavy write workloads, the storage speed reportedly fell to 1.1 MB/s, which is lower than a typical hard drive.
The same testing found the Pro Max's storage was 38% slower than the TLC-based iPhone 18 Pro. This suggests that while QLC increases capacity, it can be a bottleneck for write-intensive tasks like recording high-bitrate video or transferring large files.
This is a reported benchmark rather than an official Apple specification, and real-world impact depends on usage patterns. Still, it highlights the engineering trade-off between density and performance in consumer devices.