Well in most large corp. environments outlook is a thing so if you have no choice but to use it I'd rather use it from OS X.

Doesn't Exchange support IMAP?

Outlooks is far.ore than email. It's email, scheduling, calendars, meeting room bookings etc.. and it's all integrated. Not using outlook in a corp environment is a quick route to madness.

yes but IMAP does not help with meeting scheduling, conf. room reservations etc.

I use the Outlook web app for that.