To the best of my knowledge, the largest DDOS that has ever been successfully mitigated was mitigated by CloudFlare. The real answer, however, is that the best DDOS protection is the one that best fits your needs. There are some DDOS protection services that are too heavy handed for some use cases, and there are some that are too light to handle the attacks you might receive.
You should take any data about attacks you receive and approach different DDOS protection providers and ask them if they can mitigate that type of attack without harming the quality of the service that you host behind it. That will most likely be the most sane approach.