The pygmy cories are less 'cories' than the others. They are much more mid-level swimmers than exclusively bottom dwellers. But they require the same basic things that all other cories require.
The salt and peppers are slightly larger, and spend more time on the bottom. Being so small they can be a bit more 'reclusive' than the larger species.
The pandas are my personal favorite, they are not a classic 'dwarf' species, like the first two, but are the smallest of the 'regular' cories. They like caves to hang out in and natural plants to spawn on - mine have spawned quite regularly, but only ever put the eggs on the glass once that I've ever seen, the rest of the spawnings (as far as I know) are on the underside of leaves on broad leafed plants. They too can be rather skittish at times, given their diminutive size.
All do best in LARGE numbers. The minimum I see is generally 6, but 9+ would be far better.
The big questions are: What size is the tank? What are the parameters? And who are the potential tank mates?
I'd add, IMHO, the pandas display the most 'cory-like' behavior, followed by the salt and pepper and lastly the pygmy.