As per the title, what are the essential differences between growing plants in pots vs growing in the soil? The pots I'm talking about are not connected to the soil at their bases.
Completely determined by your locality/environment. Plants in pots are relegated to whatever we give them; soil, water, fertilizer, light, air. Plants in the garden have safeguards. Lots more available water, light (depending on the time of year), aeration, drainage, water, as well as beneficials. Hopefully a live soil. Any plant planted in a pot must have the best of whatever it is you are able to give that plant; soil, water, fertilizer and light...drainage. Plants in pots need us humans completely. The best soil, water at the correct time, fertilizer is even more critical, and given the best light possible. To use anything other than potting soil really diminishes the chances for a plant in the all time most artificial environment we humans are able to hand our plants. It amazes me that we humans are able to cough up 'permaculture'. Every plant we plant is always in an artificial environment. There is no way we could make a self replicating, self replenishing environment, no matter how hard we tried.
Plants in pots give us latitude to drag the plants indoors or outdoors depending on the environment. Plants in the garden have to deal with whatever season is afforded them.