You have phrased your post as an either/or question but it isn't really. The only container a person might plant straight into the ground outside is a peat pot, peat block or other supposedly degradable pot. I say 'supposedly' because experience shows that these pots rarely work well. They constrict roots and wick moisture away from them. Unless absolutely soaked and completely buried they can dry out like cardboard and seriously stunt the plant. Search on here for many threads about peat pots.

As for 'removing the roots and shaking the soil off' you don't need to do that either. You just turn the seedling gently out of its container and plant the whole root ball into the ground. Don't start shaking the poor thing about. If the roots have filled the container entirely you can tease the outer ones out gently but otherwise leave them alone.

Thank you for your help. Thanks great

Good info from floral above and even more in the discussion just a bit down the page titled "What is your go to container for starting seeds". And in the FAQ here about containers to use.

http://forums2.gardenweb.com/discussions/3736644/whats-your-go-to-container-for-starting-seeds-flats-pods-cartons?n=10

Most vegetables that are grown for transplanting are not started in the same size container they would go to the garden in. You start small and they are transplanted at least once into a larger container before they are big enough to go to the garden.

Dave