My experience is that if you have to maintain your own stack (which you'd need to in order to recursively walk directories) its faster to use the builtin stack than to implement your own.

Further, it seems that this would IO-bound not CPU-bound so whatever small overhead exists in recursion vs iteration will not be noticeable.

I think the difference is rather that `fd` uses threads and `ff` does not.

> `fd` uses threads and `ff` does not.

Author here. This is true. ff does not use threads right now. I have started learning Rust just a few days ago. I am not quite yet familiar with advanced topics such as achieving parallelism using threads in Rust and other similar stuff. My knowledge of Rust is limited at this moment and I struggled to get the language concepts to work such as ownership, lifetimes, etc. I am sure that I will be able to improvise the ff's performance by some extent by gaining some more knowledge of Rust.

UPDATE: Now ff also uses threads to achieve parallelism.