I find the following Ido features really useful:
- Ido "directory merging". With it you can type the (potentially partial) name of a file that resides in a different directory (that was previously visited) and Ido will, after a small configurable delay, change the path to match. I have not yet seen this capability inside Ivy.
- Ido has the ability to identify files that are "not important" and can hide or show them in a prompt. "Non important" files are output files (like object files, byte-compile files), etc.. So far with Ivy I have only been able to use patters to filter out these files. Something that is not required when using Ido.