We are currently planning and designing a huge migration of data from a custom-made application to Salesforce, integrated with Marketing Cloud.
My main concern is to know when is it convenient to migrate certain data to Marketing Cloud Data Extensions and when should it persist in Sales Cloud.
I understand that all sales data and certain marketing data has to live in Sales Cloud, like campaigns, campaign members, etc... but, for example, if I have a set of fields that are related to only specific subset of campaigns, should I then create fields in campaign members or should I create Data Extensions in MC and use AMPScript in my emails?
I am aware that this is in some sense opinion-based, but I'm sure there's a set of best practices regarding when to place stuff in one place or another.
Some of my colleagues favor putting all the data in Sales Cloud and creating 10-20 fields in Campaign Member and, if in a year we need more fields, do it again, just for the sake of having all data in the same place.
On the other hand, I don't think it's scalable because if along 5 years the client creates 10 new campaigns and each of those campaigns require 10 more fields we would end up with a massive Campaign Member entity.
So, in a nutshell, if you could help me with this issue, even if it's not with specific technical data, it would be highly appreciated :-)