[briandear]

Exact same until you need to easily deal with code formatting. Slack uses Markdown Hipchat uses nonsense. Also Hipchat's reliability is garbage: getting @mentions hours later or not at all. Hipchat is horrible. You also have audio and video calling in Slack.

[brightball]

Hipchat has AV calling. I've never experienced delayed @mentions and we've been using it for 3 years with close to 100 people.

With Slack you use backquotes for code. With Hipchat you type /code first.

Same service.