The Arcology, though appearing in-game it is over 4 times the diameter of the metropolis stations, the illustrations (ie the dockscreen image of the arcology [this also has its own bug; if one looks at the planet's day-night boundary, there are visible triangles where the faces of the planet's mesh arn't smooth. Easy to fix with a little blur-brush in gimp or photoshop though.] and the image of the Metropolis show that the metropolis stations are probably at least twice the diameter of the Arcology, if not more, based on the scale of the Antares ships around them...)
Now, taking in the scale of these stations as implied by the in-game pics, Eridani's station is simply vast in comparison to St.k's, which further implies that Eridani is a much bigger community than st.k's.
