A localized repair handles a specific failure: a torn membrane, a cracked fitting, or a failed vent seal. It is the smallest scope and fits damage that is contained.
Resealing is maintenance. Seams and edges are cleaned and renewed before water gets in. It does not fix a soft deck or a leak that has already soaked the structure.
Replacement means removing the membrane, and sometimes the deck, then rebuilding the roof. It is the largest scope and follows confirmed damage rather than a guess.
A coating is not a substitute for any of these when the deck feels soft or the source of water is still unknown.

