I go solo with an AGG "3 cup" pot - which is actually about 900 ml capacity.. With two people it's simple... take *TWO* of them. Put one in the second guy's pack - realisticly two pots are easier than one for this - and this is what I typically do with a companion. Realisticly with the lightweight small pots this is not a significant weight penalty.

With larger groups (3-4) I take a 2l pot and the little one.

In Winter I always take either the 2l pot, or my MSI set (which is about a 1.5 and a 1 liter pot together) - The latter being about the minimum size I like for melting snow for drinking - which I do in winter.