If you care about latencies or are on very low bandwidth or noisy connections preshared dictionaries matter a lot. By and large they generally always help but c

If you care about latencies or are on very low bandwidth or noisy connections preshared dictionaries matter a lot. By and large they generally always help but come with complexity so are often avoided in favor of a simpler approach whose compression is acceptable rather than optimal. But if there’s a clear and well implemented standard that’s widely adopted I would always choose preshared dictionaries. Likewise secure connections are hard and without TLS and other standards most people wouldn’t try unless they really needed it. But with a good standard and broad implementation it’s basically ubiquitous.