While using a USB webcam on Raspberry Pi has the convenience of supporting identical behavior and code on the desktop as on an embedded device, you might consider using one of the official Raspberry Pi Camera Modules (referred to as the Raspberry Pi Cams). They have some advantages and disadvantages over USB webcams.
The Raspberry Pi Cams use the special MIPI CSI camera format, designed for smartphone cameras to use less power. They have a smaller physical size, faster bandwidth, higher resolutions, higher frame rates, and reduced latency compared to USB. Most USB 2.0 webcams can only deliver 640 x 480 or 1280 x 720 30 FPS video since USB 2.0 is too slow for anything higher (except for some expensive USB webcams that perform onboard video compression) and USB 3.0 is still too expensive. However, smartphone cameras (including the Raspberry Pi Cams) can often deliver 1920 x 1080 30 FPS or even Ultra HD/4K resolutions. The Raspberry Pi Cam v1 can, in fact, deliver upto 2592 x 1944 15 FPS or 1920 x 1080 30 FPS video even on a $5 Raspberry Pi Zero, thanks to the use of MIPI CSI for the camera and compatible video processing ISP and GPU hardware inside the Raspberry Pi. The Raspberry Pi Cams also support 640 x 480 in 90 FPS mode (such as for slow-motion capture), and this is quite useful for real-time computer vision so you can see very small movements in each frame, rather than large movements that are harder to analyze.
However, the Raspberry Pi Cam is a plain circuit board that is highly sensitive to electrical interference, static electricity, or physical damage (simply touching the small, flat orange cable with your finger can cause video interference or even permanently damage your camera!). The big flat white cable is far less sensitive but it is still very sensitive to electrical noise or physical damage. The Raspberry Pi Cam comes with a very short 15 cm cable. It's possible to buy third-party cables on eBay with lengths between 5 cm and 1 m, but cables 50 cm or longer are less reliable, whereas USB webcams can use 2 m to 5 m cables and can be plugged into USB hubs or active extension cables for longer distances.
There are currently several different Raspberry Pi Cam models, notably the NoIR version that doesn't have an internal infrared filter; therefore, a NoIR camera can easily see in the dark (if you have an invisible infrared light source), or see infrared lasers or signals far clearer than regular cameras that include an infrared filter inside them. There are also two different versions of Raspberry Pi Cam: Raspberry Pi Cam v1.3 and Raspberry Pi Cam v2.1, where v2.1 uses a wider angle lens with a Sony 8 megapixel sensor instead of a 5 megapixel OmniVision sensor, has better support for motion in low lighting conditions, and adds support for 3240 x 2464 video at 15 FPS and potentially up to 120 FPS video at 720p. However, USB webcams come in thousands of different shapes and versions, making it easy to find specialized webcams such as waterproof or industrial-grade webcams, rather than requiring you to create your own custom housing for a Raspberry Pi Cam.
IP cameras are also another option for a camera interface that can allow 1080p or higher resolution videos with Raspberry Pi, and IP cameras support not just very long cables, but potentially even work anywhere in the world using the internet. But IP cameras aren't quite as easy to interface with OpenCV as USB webcams or Raspberry Pi Cams.
In the past, Raspberry Pi Cams and the official drivers weren't directly compatible with OpenCV; you often used custom drivers and modified your code in order to grab frames from Raspberry Pi Cams, but it's now possible to access a Raspberry Pi Cam in OpenCV in the exact same way as a USB webcam! Thanks to recent improvements in the v4l2 drivers, once you load the v4l2 driver, the Raspberry Pi Cam will appear as a /dev/video0 or /dev/video1 file like a regular USB webcam. So, traditional OpenCV webcam code such as cv::VideoCapture(0) will be able to use it just like a webcam.