The best choice of ELB by use case
One item of note when using AWS is that you don't see version numbers. There is no such thing as S3 version 1.0 and S3 version 2.0. At any given point in time, AWS offers the best version of a given service, and upgrades happen transparently. This puts a tremendous responsibility on AWS, but it makes our job easy. The fact that AWS still offers three load balancers instead of just one tells us that they see value in offering all three. And all three still exist because each could be the best for the job depending on the use case.
And that's the perfect segue. CLBs are probably the best option for legacy applications where a CLB is already in place. Many deployments were done when CLBs were the only option (at that point, they were called ELBs when that was the only option). Only later were they renamed CLBs to distinguish them from the new ALBs.
If your deployment already uses CLBs, but you are considering migrating to ALBs, these are usually...