Circular saws are extremely portable.
The cut’s accuracy depends on your ability to steadily move a 15-pound tool, which has a motor spinning a blade at high RPMs.
There can be some kickback when the blade bites into the wood, but because you only need to stabilize the wood and not the saw itself, it’s easier to manage.
Miter saws, unlike circular saws, are stationary.
If you need a saw that is cheap, portable, and can make a lot of different types of cuts, you need a circular saw. If you need to make a lot of accurate cuts, especially cuts that are angled or beveled (or both), you need to get a miter saw.