there is only 2 inch difference in the pots, but they vary in depth. A 6' pot is roughly 6-8" deep. A 10" pot is almost afoot deep, hence the difference in what they hold. although the pot looks only a tad larger, the volume it holds is WAY more than it looks.
that's what the store mngr at target told me when I hounded him on it. he had to look it up in his delivery book, I hope he wasn't just talking out jhis ass.