This is an interesting question, and I think the answer depends on what your primary goal is. Istvan makes good points in favor of straight-forward C (integrated with Python) for building tools that are easy for others, without a ton of experience in programming languages, to modify etc. However, if your primary goal is to make efficient and robust tools for others to use, then let me offer a somewhat different perspective.
The language in which one develops a project has important implications beyond just the speed and memory profiles that will result. Both C++ and Rust will allow you to write very fast tools, making use of zero-cost abstractions where feasible, with predictable and frugal memory profiles (assuming you choose the right algorithms and are careful in designing the programs). However, two important areas where I see these languages diverging are safety and maintainability. By safety, I mean minimizing the types of nefarious memory and correctness bugs that can easily slip into "bare-met