Bill Troop, co-autor of the development cookbook (or similar tiltle) and TF-2, TF-4 fixers posted a long thread in rec.darkroom news group of why alkali fixers.
In short, he says (but many did not agree) it washes better.
Usually they are not hardening fixers (but it could be done).
Since they do not smell, I decided to use it for paper.
For films, I use an acid hardening fast fixer.