I have pens as they were so much easier to get hold of than NIC cubes.
The buns have an XL dog crate with an 8-panel pen attached as their base (making 9ftx3ft in total, though the doors are always left open and they free-range in the living room).
Then we have an 8-panel pen that we use as a fence (we took off one set of 'hinges' to open it out) that fences off the area of the living room that has the computer/ telephone/ lamp/ antique chest of drawers in.
Then in our conservatory another 8-panel pen split into two 'fences' of 4 panels each, which fence off the piano at one end of the room and random stuff at the other end.
Finally we have a 6-panel drop-pin pen: 4 of the panels fence off the TV in the living room, and the remaining 2 panels are used to block off the conservatory doors when we open them.
I would recommend the 8-panel pens, as they're much better value for money than the 6-panel drop-pin pens. Also, because of how the drop-pin pens are hinged together, they can only really make hexagon shapes (you can't use them for straight fences, or a rectangular shaped pen). Whereas the 8-panel pens can be straight/rectangles/octagons, etc.