The CPU's load/store unit is usually designed with SIMD in mind, and the access width is 16 bytes (or 32 bytes for Haswell-and-later Intel CPUs). This means you

The CPU's load/store unit is usually designed with SIMD in mind, and the access width is 16 bytes (or 32 bytes for Haswell-and-later Intel CPUs). This means you get more bandwidth by using SIMD.