README.md in google-cloud-dialogflow-v2-0.6.4 vs README.md in google-cloud-dialogflow-v2-0.7.0

@@ -4,10 +4,16 @@
 
 Dialogflow is an end-to-end, build-once deploy-everywhere development suite for creating conversational interfaces for websites, mobile applications, popular messaging platforms, and IoT devices. You can use it to build interfaces (such as chatbots and conversational IVR) that enable natural and rich interactions between your users and your business.
 
 https://github.com/googleapis/google-cloud-ruby
 
+This gem is a _versioned_ client. It provides basic client classes for a
+specific version of the Dialogflow V2 API. Most users should consider using
+the main client gem,
+[google-cloud-dialogflow](https://rubygems.org/gems/google-cloud-dialogflow).
+See the section below titled *Which client should I use?* for more information.
+
 ## Installation
 
 ```
 $ gem install google-cloud-dialogflow-v2
 ```
@@ -63,13 +69,71 @@
 end
 ```
 
 ## Supported Ruby Versions
 
-This library is supported on Ruby 2.4+.
+This library is supported on Ruby 2.5+.
 
 Google provides official support for Ruby versions that are actively supported
 by Ruby Core—that is, Ruby versions that are either in normal maintenance or
-in security maintenance, and not end of life. Currently, this means Ruby 2.4
+in security maintenance, and not end of life. Currently, this means Ruby 2.5
 and later. Older versions of Ruby _may_ still work, but are unsupported and not
 recommended. See https://www.ruby-lang.org/en/downloads/branches/ for details
 about the Ruby support schedule.
+
+## Which client should I use?
+
+Most modern Ruby client libraries for Google APIs come in two flavors: the main
+client library with a name such as `google-cloud-dialogflow`,
+and lower-level _versioned_ client libraries with names such as
+`google-cloud-dialogflow-v2`.
+_In most cases, you should install the main client._
+
+### What's the difference between the main client and a versioned client?
+
+A _versioned client_ provides a basic set of data types and client classes for
+a _single version_ of a specific service. (That is, for a service with multiple
+versions, there might be a separate versioned client for each service version.)
+Most versioned clients are written and maintained by a code generator.
+
+The _main client_ is designed to provide you with the _recommended_ client
+interfaces for the service. There will be only one main client for any given
+service, even a service with multiple versions. The main client includes
+factory methods for constructing the client objects we recommend for most
+users. In some cases, those will be classes provided by an underlying versioned
+client; in other cases, they will be handwritten higher-level client objects
+with additional capabilities, convenience methods, or best practices built in.
+Generally, the main client will default to a recommended service version,
+although in some cases you can override this if you need to talk to a specific
+service version.
+
+### Why would I want to use the main client?
+
+We recommend that most users install the main client gem for a service. You can
+identify this gem as the one _without_ a version in its name, e.g.
+`google-cloud-dialogflow`.
+The main client is recommended because it will embody the best practices for
+accessing the service, and may also provide more convenient interfaces or
+tighter integration into frameworks and third-party libraries. In addition, the
+documentation and samples published by Google will generally demonstrate use of
+the main client.
+
+### Why would I want to use a versioned client?
+
+You can use a versioned client if you are content with a possibly lower-level
+class interface, you explicitly want to avoid features provided by the main
+client, or you want to access a specific service version not be covered by the
+main client. You can identify versioned client gems because the service version
+is part of the name, e.g. `google-cloud-dialogflow-v2`.
+
+### What about the google-apis-<name> clients?
+
+Client library gems with names that begin with `google-apis-` are based on an
+older code generation technology. They talk to a REST/JSON backend (whereas
+most modern clients talk to a [gRPC](https://grpc.io/) backend) and they may
+not offer the same performance, features, and ease of use provided by more
+modern clients.
+
+The `google-apis-` clients have wide coverage across Google services, so you
+might need to use one if there is no modern client available for the service.
+However, if a modern client is available, we generally recommend it over the
+older `google-apis-` clients.