Fastest? A lot of them claims to be the fastest. But would you use a "fast" blockchain, or a blockchain that is secure? I am sure you will be willing to use a chain that is actually secure. After all the information about your coins are stored in the chain. And most of the "fast" and "scalable" chains are mostly centralized. You don't want to be own a large amount of those coins because the risk of the chain getting tampered is high. Instead of looking for the fastest blockchain, stick with the ones that are currently well known. A little slow, but worth waiting.