Which office software to choose for university and day to day tasks?
Your Microsoft choices are listed here.

Main differences are, the online version and the fully installed on your hard drive.

Microsoft Office 365 (it is a online app), lower cost and 4 Years access.

Microsoft Office 2011 (on you hard drive)- no need to go to Internet.

Free app: Open Office, does almost everything Microsoft Office does.

I have the Office 2011 on my MacBook Air, it works like a charm (PowerPoint, Excel, Word), but stay away from the Outlook Email, and use the build in Apple Mail instead.