Amazingly, the biggest issue with Office 365 is not how to use it, nor how to implement or deploy it, but rather trying to determine the right plan for the organization.
As you're building your strategy for selecting the right plan to fit the needs of the business, it would be nice to have a tool devoted to making selection easier. Fortunately, Microsoft has recently released such a tool, the Office 365 Plan Selector Tool.
The Office 365 Plan Selector Tool starts with a series of questions, and then, based on your input, recommendations are given which include descriptions, reasons why the plan was selected, and also proposed pricing. And, if the plan doesn't exactly fit, or the cost is too high, you can always go back and start again.
The tool is meant for Microsoft Partner assistance, but anyone can download it and use it. The download is available as an Excel spreadsheet, but is heavy with Macros that execute the content as an app.
The download is here: Office 365 Plan Selector Tool