But the truth about light may really be "neither". This paper explores an obvious variation on the existing models: light not as a "thing" (e.g. amplitude, phase, energy), but rather as a "process? (i.e. the propagation process).
Imagine two steps: a period of expansion/extension, followed by a period of contraction/collapse. Such a model turns out to be extraordinarily rich with implications. All of the familiar features of special relativity theory follow without mystery: apparent clock slowing, length contraction, velocity limitation, etc. In addition, important features of general relativity theory also follow: apparent gravitational effects on clocks, gravitational red shifts, light bending, etc.