I guess it depends whether you transcribe how it is spoken or how it is written, letter by letter.
Sometimes there is no single correct answer for how to transcribe something because of the inherent limitations of the Latin alphabet, for instance having only five main vowels (a, e, i, o, u) whereas many languages have more diverse vowel sounds, so you just pick the closest approximation or combination. But what do you do with vowel sounds that land pretty much exactly in between two of them? In those cases two different spellings can be equally correct and you just have some arbitrary convention on which one should be predominantly used.
Also, different regional Arabic dialects probably have different pronunciations too.