I prefer the 5series for its style and its size. Plenty of room in back for a few kids, trunk is roomy enough to hold a mother in law.
The 540i has all the goodies that the 7 does unless you want a fridge in the backseat or a 12 cylinder. The trunk is bigger so it will hold a "family sized" mother inlaw and have room left over for groceries.
If I where to give up the 5 it would be for an 8, I would rather have a 2 door, and I don't have mother inlaw issues any more.