On a PC, if it is near to the router, most people use ethernet (wired connection) instead of wireless because ethernet is faster and more reliable than a wireless connection.
If you must use wireless on a PC, it's best to use a USB type so you can plug it in on the top of computer desk via a hub, or plug it in to the front USB port on the PC, thereby giving the device the best chance of connecting to the router.
If you fit a wireless PCI card, it's going to be buried low down at the back of the PC which would probably affect the quality of the wireless connection to the router.
The only downside to using a USB wireless device is that it occupies a USB port which could be used for something else, which is why the PCI card solution is often used instead even though it may not be the best choice.