I’m the wrong person to ask, all I know is that Microsoft, Azure and Offfice365 is on the government list of places we can put our data (which doesn’t go above NSIS level 3) safely and legally. Slack isn’t on that list.
Apart from some abstract legal paperwork requirements like those, I honestly don't see much difference between both privacy wise. If the company really requires privacy and owning their data, they should setup some hosted slack clone themselves.
AFAIK, Slack will store user data on servers in the US. For most European countries (if not all), Microsoft can guarantee that data won't leave that country. Especially for privacy sensitive sectors (e.g. finance), that can be a hard requirement.
They can still guarantee to store it in the EU, which should legally be enough for any EU company. I don't think laws are allowed to require storing data in a specific member country.
It's not that a company owns their data, or needs privacy, its that they need tools to discover customer or even non-customer data from across the entire suite of systems that they use. It's a tremendous amount of data and MS built tooling that helps do that across all of their services.
Setting up some kind of hosted solution in a country to comply with data sovereignty laws might be a solution, but it becomes a data island that makes compliance with other regulatory regimes that much harder.
You can literally pull every single conversation private or not from Slack with a button push or email request. The company owns all that data. There doesn't appear to be anything special about how Teams does data retention from my perspective.
Again, it's not about the company owning the data.
For instance, regulatory requirements might mean that someone comes to you and says...give me every interaction and related data that references this person who doesn't work here. That would mean anytime they are mentioned in word docs, records in Salesforce, anytime someone mentioned them in chat or email, and everything else.
I'm not saying that you aren't right. I'm just saying that the integration with other services allows for management at scale that is useful in large organizations.
Instead of going to lots of individual services and exporting data into something that you can then use to ad-hoc query, you can go to one place and create a job that goes out and collects the data for you. That has value.
In the end it gets back to the "best of breed" vs "pre-integrated"...It depends on how and where you assess value.
For some people, just not using MS has value. For lot's of people/orgs having all the things integrated already, even if they aren't the best tools available, is a better value.
