Update functions_vs_classes.md text so it's not empty any more and provides useful information and links

doc/explanation/api/functions_vs_classes.md

@@ -1 +1,20 @@
 # Functions vs. Classes
+
+## Development Flow
+
+As you gear up to develop your Panel application, you'll encounter a couple of initial decisions to make regarding **approach** and **environment**:
+
+1. **Programming Approach:** Will you opt for a Python *function-based* approach or a *class-based* approach?
+   - The function-based approach is recommended for new and basic users. It utilizes `pn.bind`, as you've already experienced while [building a simple app](build_app.md).
+   - The class-based approach is recommended for intermediate Panel users who aim to construct larger and more maintainable apps, as well as reusable components.
+
+   Interested in a class-based approach instead?
+
+   Explore the same ['outlier' app built using a class-based declarative API](../explanation/api/examples/outliers_declarative.md). Study the [Explanation > APIs](../explanation/api/index.md) section for a detailed discussion on each of the API options.
+
+2. **Development Environment:** Will you develop in a notebook or in an editor environment?
+   - If you're unsure, starting in a notebook is recommended as you familiarize yourself with Panel. However, you can switch between them at any time.
+
+Please refer to the [Getting Started > Core Concepts](../getting_started/core_concepts.md) for more info.
+
+This [Best practices document](../getting_started/core_concepts.md) contains some examples of do's and don'ts that involve classes.