App Lab vs. App Store - What to Choose for Public Testing?

App Lab is marketed as a good solution for putting out experimental builds of projects. The Store already has concepts like Release Channels and user whitelisting. Are there any additional advantages to using App Lab over the Store for development? We anticipate playtesting with external users at various points, including phases with closed and open invitation lists. Should we, for example, use App Lab to run external playtesting and then have our published build go through the Store? What would Oculus recommend as the preferred process?