Another thing to consider when discussing multi-provider and single provider is that even the single provider can use multiple solutions in a mesh to provide coverage (or use methods such as any-casting to spread the load). The point here is that we are really talking about single coordination – having an employee or outsourced provider ensure that the attack is handled in the most effective way possible for any attack type. From there, it is just about ensuring that the mitigation capabilities are sufficient and everyone understands the plan.
If you have zero tolerance for downtime, then a combination of on-premise and off-site solutions will work best. Regardless of whether they are multi- or single provider, fast, accurate and automated initial responses are critical. If you have a low tolerance for downtime (say, under 10 minutes), then an off-site service from a single provider will get you what you need. If you can accept some downtime, then a multi-provider scenario will provide you with an acceptable alternative. In reality, your business will drive what makes the most sense.