For the past 7 years, my employers have only provided me with a laptop for a work computer. Whether in the office or working from home, I always use an external monitor, mouse and keyboard. With those items attached to my laptop (I use a dock to make things easier), it functions nearly indistinguishably from a desktop computer. Since it's a work computer, I don't use it for gaming but I run compilers, VMs, Excel, Word, Visio, PowerPoint and all types of other software on it. The main advantage to having just the laptop is that I can move from place to place and bring my setup with me. In my current job, I often travel to remote client sites and work on-site but other times, I work from my home. Portability is the main reason for this setup and it works fine.
However, if I didn't require portability, I would choose a desktop over a laptop every time. The cost to performance ratio for a desktop is much better than a laptop. A desktop is easier to maintain, repair and upgrade and has better storage options. Although I own several personal laptops, I always prefer using my desktop at home.