Design-Build-Test-Release. Being able to work through the development cycle quickly (and meaningfully) can be the difference between a successful product and a failure.
Rapid Prototyping starts with strong design. Depending on what your sprint or overarching objectives are - the interaction model, use-cases, accounting for the type of behavior that may be happening in the margins - knowing which way to go or what combination of techniques to use goes a long way.
FAST -> FASTER -> FASTEST