AD455 - the fall of the Roman west?

[Robert Vermaat]

After AD455, then, the western empire ceased to be a viable political entity. It was no more than an appendage of the eastern empire, manipulated by ambitious generals: a kind of zombie polity that staggered on for another twenty years, with only the occasional appearance of independent life. The final extinction of the imperial line in 476 was no more than an afterthought.

Yes and no. Indeed it's and age-old question, and I guess answers depend on how you ask the question. For instance, many scholars take Adrianople or the accession of Theodosius as the start of the 'Byzantine' Empire. Others have taken the fall of Rome in 410 as the sign of the end. Or indeed 476, or 480. For me it's actually 474, when the Patricius Gundobad rather returns home to Burgundy and succeed to the Burgundian Kingdom after the death of his father, than remain in Rome and rule the Western Roman Empire.

In your definition, 455 signified the end because after that the West was a puppet of the East. Was it? Indeed the West was severely weakened after the Vandal attack, but it was not exactly powerless. Maioran comes to mind, and several actions by other armies, even though localised sometimes.
And if you think about it, wasn't Honorius as powerless without aid from Constantinople too? Especially after the death of Stilicho, the West can be seen as a diminished Empire. By that definition, 408 would be as good as 455?