Hi @CMayer,
Big, loaded question 
This really comes down to the process and data requirements, what the connectors between the solutions look like etc. Depending on each situation, I’d recommend evaluating the expected invest for development and maintenance. These decisions are not to be made lightly since their implications will accompany you for years, probably – there isn’t a one-size-fits-all approach, I’m afraid.
This is however also the beauty of HubSpot. Over the years, the amount of options and the toolkit for developers has grown.
Other users are much more knowledgeable when it comes to developing, the developers board in the community is a great place to explore specific problems.
Best regards!