The principal difference is that rust constrains aliasing somewhat more than c. The practical differences currently are more relevant to compilers than cpus, s

The principal difference is that rust constrains aliasing somewhat more than c. The practical differences currently are more relevant to compilers than cpus, since architectures do not provide a way for programs to provide aliasing information to the cpu, and so cpus do their alias analysis dynamically, in a way that works as well for rust as for c. But one can imagine an architecture which allowed programs to supply aliasing information statically. This would be relevant for both c and rust, just somewhat more so for rust.