Added a "Why use zend-mvc?" section

Also edited the other areas of the text covering zend-mvc for content.

Author: weierophinney

doc/book/why-expressive.md

@@ -1,17 +1,35 @@
 # Should You Choose zend-expressive Over zend-mvc?
 
-After creating several projects with zend-expressive, we recommend that you
-choose Expressive for any new project — _if the choice is yours to make_.
+We recommend that you choose Expressive for any new project — _if the
+choice is yours to make_.
+
+## Why Use zend-mvc?
+
+zend-mvc is a proven platform, with half a decade of development behind it. It
+is stable and battle-tested in production platforms.
+
+Because it is opinionated about project structure and architecture, fewer
+decisions need be made up front; developers know where new code goes, and how it
+will wire into the overall application.
+
+Additionally, a number of training courses exist, including [offerings by
+Zend](http://www.zend.com/en/services/training/zf-fundamentals-i), allowing you
+or your team to fully learn the framework and take advantage of all its features.
+
+Finally, zend-mvc has a lively [module ecosystem](https://packagist.org/search/?q=zf2),
+allowing you to add features and capabilities to your application without
+needing to develop them from scratch.
 
 ## We Recommend Expressive
 
 [zend-mvc](https://github.com/zendframework/zend-mvc) has many preconceptions
-about how things work, yet they're very broad and unspecific.  What’s more, it
-also has several pre-wired structures in place.
+about how things work, yet they're very broad and general. What’s more, it
+also has several pre-wired structures in place that may either aid you —
+or get in your way.
 
 As a result, you are required to know a lot of what those things are — *if* you
-want to use it optimally.  And to acquire that depth of knowledge, you’re going
-to need to spend a lot of time, digging deep into zend-mvc’s internals, before
+want to use it optimally. And to acquire that depth of knowledge, you’re going
+to need to spend a lot of time digging deep into zend-mvc’s internals before
 you begin to get the most out of it.
 
 To quote Zend Framework project lead, [Matthew Weier O’Phinney](https://mwop.net):
@@ -29,25 +47,27 @@ on the other hand, comes with barely any of these assumptions and requirements.
 It provides a very minimalist structure. Essentially all you have to become
 familiar with are five core components. These are:
 
-- A DI container
-- A router
-- An error handler for development
-- A template engine (if you’re not creating an API)
-- PSR-7 messages and http-interop (future PSR-15) middleware
+- A DI container.
+- A router.
+- An error handler for development.
+- A template engine (if you’re not creating an API).
+- PSR-7 messages and http-interop (future PSR-15) middleware.
 
-Given that, you can quickly get up to speed with the framework and begin
-creating the application that you need.  We believe that this approach — in
-contrast to the zend-mvc approach — is more flexible and accommodating.
+In many cases, these are provided for you by the skeleton, and do not require
+any additional knowledge on your part. Given that, you can quickly get up to
+speed with the framework and begin creating the application that you need. We
+believe that this approach — in contrast to the zend-mvc approach —
+is more flexible and accommodating.
 
 What’s more, you can mix and match the types of applications that you create.
 
 - Do you just need an API? Great; you can do that quite quickly.
 - Do you want an HTML-based front-end? That’s available too.
 
-When building applications with Expressive, you can make use of any other
-Zend library, or non-Zend library.  You can pick and choose what you need, as
-and when you need it.  You’re not bound by many, if any, constraints and design
-decisions.
+When building applications with Expressive, you can make use of the various Zend
+components, or any third-party components or middleware. You can pick and
+choose what you need, as and when you need it. You’re not bound by many, if
+any, constraints and design decisions.
 
 ## In Conclusion