There isn’t really a right versus wrong answer here. Similar to selecting a toothpaste, this is a choice that is usually based on preference.
Patients who will be less compliant with putting something in their mouth every night before sleeping would likely benefit from having a fixed retainer. On the flip side, patients with poor compliance would also have a problem with having to use a floss threader everyday to clean underneath the fixed retainer.
Clear removable retainer
However, a clear removable retainer would be a great option for a patient who is willing to use the retainer every night, because they will also be able to brush and floss much easier without having the retainer in the way.