Desktops have better displays, better keyboards, better everything. I've taken laptops on deployments, and my wrists felt the hours spent typing away on it at that odd angle. It was bad enough that I bought a "natural" keyboard for my desktop after I returned home from the first one. I have a mechanical (switch) keyboard, and that's far superior to any laptop keyboard ever made. Frankly laptop keyboards suck!

Lets list the advantages of each.

Desktops:
- Better displays. Can also do multiple monitors.
- Better keyboards. Have the option to upgrade to the best - a mechanical switch keyboard. Laptop keyboards don't hold a candle to those, and it isn't close.
- Upgradable. As long as the case stays intact, you can upgrade a desktop indefinitely. You can also replace faulty items yourself. For example, if one of your monitors dies, you just buy a larger one to replace it.
- Component longevity. Better cooling means the devices will last longer, increasing MTBF.
- Easier to do "power computing."
- Security. It's harder to carry off a desktop than a laptop.

Laptops:
- Portability.

Would say that if all you do is email & web surfing, then a laptop is probably your best option. You really don't want to spend many hours working on a laptop. Desktops are a much better option for serious computer work.