Which is better: script or animation (which needs to change with scripting)?

My project has some objects that I load at runtime. Some of them need to be animated. A simple bounce for example. And the speed and amplitude of that bounce needs to be alterable at runtime too. There may be many such objects.

Is it better to conditionally attach a ‘movement’ script to such objects, and script that movement (using standard math/trig), or use the Animation Editor to create the movement, then (somehow) access those curves and alter them as needed?

Better is defined in terms of performance (runtime speed and memory footprint) rather than simplicity of implementation.

in personal experience using Blender to create animations, i would use scripts, unless your good at creating animations. Also it depends on what your animating, Ex: a walk animation vs a cube bouncing up and down. it would probably be best to use both for certain situations.