In my opinion planting in the ground is better unless your native soil is completely terrible, or if you want/need to be able to move your plants for whatever reason. Even if your native soil is not very good as long as the drainage is reasonably good you can dig a hole and fill it with amended soil.
Growing in the ground is far more water-efficient as well, which makes growing easier and cheaper. More responsible water usage is becoming increasingly more important on the west coast with our mega-drought going on. I get frustrated by people growing crops like almonds that have high water needs here in California. I feel we should all be working towards lessening the impacts that growing pot has on our resources, if for no other reason than for the image of the pot-growing community to those who wish to delegitimize your right to grow your own weed. Growing in the ground is a way of lessening water usage without sacrificing quality or quantity. If you have good enough drainage growing in the ground can sometimes result in bigger plants as your plants will never become rootbound.
A third option to the two already discussed(in a pot or digging a hole and putting it straight into the ground) and probably the best in my opinion is growing on mounds. The biggest plants I see are grown in/on mounds of amended soil on top of the native soil, with drip irrigation coiled around the mounds. You get infinite root space, as well as better aeration and superior drainage compared to growing in pots or in the ground, and mounds are easier to keep evenly moist than fabric pots at a far lower cost.
The only downside to growing on mounds as opposed to growing in the ground is if you have height restrictions. The same height issues apply to growing in pots also.