docs: improve description of different completion scripts

Author: bnjmnt4n

docs/install-and-setup.md

@@ -198,24 +198,36 @@ $ jj config set --user user.email "[email protected]"
 
 ## Command-line completion
 
-To set up command-line completion, source the output of
-`jj util completion bash/zsh/fish`. Exactly how to source it
-depends on your shell.
-
-Improved completions are also available. They will complete things like
-bookmarks, aliases, revisions, operations and files. They can be context aware,
-for example they respect the global flags `--repository` and `--at-operation` as
-well as some command-specific ones like `--revision`, `--from` and `--to`. You
-can activate them with the alternative "dynamic" instructions below. They should
-still complete everything the static completions did, so only activate one of
-them. Please let us know if you encounter any issues, so we can ensure a smooth
-transition once we default to these new completions.
-
-!!! info "Why are the improved completions not the default?"
-
-    To generate the dynamic completion script, execute `jj` with `$COMPLETE` set
-    to the name of your shell (see examples below). See the upstream clap issue
-    [#3166][clap] for the explanation.
+Jujutsu provides 2 different command-line completion scripts.
+
+### Standard completions
+
+The standard completion script provides completions for `jj` subcommmands and
+options.
+
+### Dynamic completions
+
+The dynamic completion script provides completions for `jj` subcommands and
+options, as well as additional completions, including bookmarks,
+aliases, revisions, operations and files. Dynamic completions can be context
+aware, for example they respect the global flags `--repository` and
+`--at-operation` as well as some command-specific ones like `--revision`,
+`--from`, and `--to`.
+
+Dynamic completions are not the default/only option since the underlying engine
+[is still labelled unstable][clap]. We expect to transition to them as the
+default once the engine is stabilized. Please let us know if you encounter any
+issues with dynamic completions.
+
+!!! info "Which completion script should I use?"
+
+    Generally, dynamic completions provide a much better completion experience.
+    Although the underlying engine is deemed unstable, there have not been many
+    issues in practice. Dynamic completions are the preferred option for many
+    contributors and users.
+
+    We recommend using the dynamic completion script, and falling back to the
+    standard completion script if there are any issues.
 
 <!-- The content tabs formatting below is optimized for the website and not for GitHub. -->