Q:

Valid measurements for the decision whether to implement a web application as SPA or MPA

I'm looking for valid measurements for the decision whether to implement a web application as SPA (Single Page Application) or MPA (Multi Page Application).
Which questions should be answered to get the right decision?

A:

What are your requirements?
This is the question you need to answer.
With that answer you can measure the implementation choices for fit.
Details
By what are your requirements I mean a whole range of things:

Functional, What process does your application support and how does it do that?
Operational, What sort of service reliability guarantees do you need to support? What sort of delivery methods are required, and need support?
Developmental, What sort of developer organisation and culture are you trying to support?

In this case, what you can functionally do by a webpage can be functionally achieved by both a Single and Multi page implementations.
Operationally the service level guarantees that are possible differ drastically between single and multi page applications. If it needs to be available even when the network disconnects, then Single Page is the way to go. However if it needs to be available across the broadest array of devices possible then multi-page apps shine as they do not require so many client side resources.
Developmentally the experience of developing a single page application is pretty similar to developing a gui client application using the os as a platform, which suits being controlled by a single team very well. While multi-page web apps can be much more distributed following a more micro-servicey architecture, which allows several teams to maintain aspects of the web application more or less independently. 

