Slack is very important to a lot of companies and groups. We use it not only as an IRC replacement, but also to hook into our CI and git repos. Along with the wealth of information and tools already put in there, there is the mindset that Slack is our communication tool we can rely on.

Google does not have a good track record when it comes to supporting their products. Look at Picasa, Google Glass, Bump, Currents, and sadly, Google Reader.

Google is good at advertising, email, and search. But I would not put any investment of time or data into their other products if I knew I needed them in the future.