What do you use a computer for?
That's the most major question that will determine what you need. While there are practical and spatial things (i.e. size of your apartment, amount of time you travel, etc) that will go into the determination, whether or not you need a desktop or can get by with a laptop (or even get by with a tablet) is primarily based on what do you use a computer for?
If your primary usages is consumption--reading emails, browsing the web, listening to music, i.e. consuming digital content of others, than a laptop is just fine.
If your primary usage is creation--making videos, recording music, writing long documents, coding or more advanced or proprietary software functions (i.e. a company VPN or secure communication network setup) than a desktop might be better suited for your needs.