This is the kind of rubbish some manufacturers attribute to their "alkali" fixer.

1 Alkali fixer regulates the pH level of the development process.

As development takes place before fixing that's just not possible.

2. Alkali fixer will maximise the tanning and staining qualities of staining developers.

Again no fixer can add anything to the tanning or staining properties. If anything the more alkali a fixer is then the more softening of a tanned emulsion in the fixer bath. Strong acids may reduce the stain created during development but most commercial fixers are pH 5.2 to 6.5 and have no detrimental effects.

3. Alkali fixer has a much greater capacity than acid fixers

Capacity isn't directly related to pH and for archival permanence fixers aren't used to their full potential capacity.

Another manufacturer/supplier compares their Alkali Rapid fixer to "conventional Sodium Thiosuphate (Rapid) fixer", but Rapid fixers are based on Ammonium Thiosuphate so the data sheet does make you wonder how much of it is correct.

There's little or no odour with most Ammonium thiosulphate based fixers between pH 5 and 7, below pH 5 the sulphur smell increases higher than 7 and ammonia becomes noticeable.