Teams and Skype for Business Online both capture IM conversation records that can be found by Office 365 eDiscovery (content) searches. All of which is good, but if you ever get around to performing eDiscovery and need this information, you’ll find that Skype for Business Online conversation transcripts are easier to use than the individual copies of conversation contributions captured by Teams. https://www.petri.com/office-365-conversation-records-ediscovery
Thanks for that @Tony Redmond, an interesting read. I don't really have many clients that have shown much interest in eDiscovery (yet), however if some of the organisations I work with were aware of this, I wonder if that would sway their decision to implement Teams over using Skype for instant messaging.
I'm not sure that it makes a whole heap of difference when the choice comes to implementing Teams. At the end of the day, if you're running an eDiscovery case, you'll have to collect, analyze, and understand data. Once you know the conversation identifier, you can find all the messages in a conversation and assemble them in order. It's easy, if it takes more time than a Skype transcript does. But it is more than doable, which is all that really matters.