The "amount of legacy comments and history" is the single most useful thing about Slack, imo. Teams in comparison was an absolute nightmare to try to find references to old conversations in, it felt like throwing away information into a bog, never to be retrieved ever again. Slack's archival search was the biggest reason I was able to onboard to a new team as quickly as I did, especially given WFH, since it removed the need to ask an actual person about so many of my questions.