Speed wise they are comparable to GNU Parallel. So the argument for Rust could be speed.
The argument against Rust could be backwards compatibility: How would you do the {= perl expr =} thing? Will it run on the current targets (CentOS 3.9 according to https://www.gnu.org/software/parallel/parallel_design.html#O...)? Will it run on systems for which you as a consultant do not have access to a Rust compiler for?