What to choose and when: web content, dynamic list entries, or a specific model?

I find Liferey's concepts to be quite confusing.

When I add new elements, I do not know what to choose:

• Using web content concept with template and structure
• Use dynamic list entries
• Use a specific model (using the services constructor).

All of them are really similar and can achieve the same goals.

Do you have any hints or tips on which concept to choose when you are developing new features in Liferay?