One difference is that liveview / reflex are stateful whereas Hotwire (turbo) is not. This has varying performance implications. Turbo will do repeat work server side and payloads will typically be bigger, however development may be simpler due to lack of state and memory usage server side may be lower.

Turbo also has the possibility to gracefully degrade when js is not available (although I doubt this will be taken advantage of much in practice).

This is a great point. Plus not all platforms, hosts, and proxies for that matter will allow web sockets.

Especially for an established rails app, allowing web sockets can require architecture changes.