I'd like to ask a purely hypothetical question, applied to this scenario... Had this pilot been equipped with ADS-B "out" and no SPOT or other alternate means of satellite communication/alerting methodologies, what would have been the sequence of events for finding him? Let's make an assumption that he was being tracked by ATC at some (or most) of the flight. Would it have helped or not? Would it have been better/easier to find him? If so with what tools?

Is ADS-B 'out' a reasonable alternative to SPOT or is it just riddled with too many limitations (perhaps your mileage will vary depending on the ATC coverage in your area and the tools for tracking)?