We have a family of 8, and often bring 1 or 2 other family members.
We absolutely hate splitting rooms. Disney does not guarantee that you will be together, and we have even been placed in different buildings! So we will prefer being crammed together in a 2-room, or GV.
Things to consider. Who will sleep where? and how many bathrooms. Some 2-room villas only have bathrooms in the "rooms". Some also have a 3rd in a living area, which helps SOOO MUCH. Kidani, Bay lake, have a 3rd. Some masters have a bathroom with a "public" door, like boardwalk, vwl, saratoga, gf.
When my kids were younger, they would literally sleep wherever, but now that they are older, they are more picky about privacy, and "space". hahaha. So the last couple years, we moved up to the OKW Grand Villa. Its cheaper then some 2-bedroom villas.... and tons, and tons of space.