So, as someone who has only dabbled in Pony, and Rust, I'll try to give an answer. With Rust, you have to fight the borrow checker, and either work out lifetime

So, as someone who has only dabbled in Pony, and Rust, I'll try to give an answer. With Rust, you have to fight the borrow checker, and either work out lifetimes manually, or just copy stuff around 'by hand' -- In reality, the whole set of traits to automagically copy stuff around doesn't work. In addition, the mental overhead of Cells, mutable cells, Rcs, and ARCs, is a lot. Pony normally works out of the box, because quite a bit can just be passed by value. You can pass by reference using reference capabilities, but there's a lot less cognitive overhead there, and a lot less fighting the compiler. I think, in the future, Pony could even derive the capabilities required automagically in many cases. I'd say the biggest issue is less around safety, but around the I/O, and FFI models.