Pot size is important, especially if you're growing organically.
A plant should be transplanted once it reaches 2.5 times the height of its current container.
Overgrown plants require more frequent irrigations, and can become more susceptible to insect problems. They can also become stunted, negatively affecting crop finishing times and yields.
The only caveat: if you're growing hydroponically, pot size doesn't matter.
Hydroponically-grown crops are irrigated up to a dozen times a day with a nutrient-rich solution, so their roots don't need much space to hunt down water and food.
In organics, however, the bigger pot, the better.
Make sure to transplant on time!