City is the thematic title under which most Town-related System sets were released from 2005 and onward. There are numerous sets that are associated with Construction, Police, Fire, Emergency, Train, Airport, Transportation, Cargo, Traffic, Coast Guard, Farm, Great Vehicles, Mining, and Space. European catalogs featured another theme called City in the years 1999 to 2000, which was referred to as City Center in American catalogs.
The remainder of the build is the control tower and terminal building. First there is a metal detector screener leading to the waiting/secure area of the airport, which seems taller than it needs to be for the minifigures. I think the same effect could have been made with half the height, except that would not allow for an impressive height for the overall tower. However it does seem to be similar to many modern airports with the high ceilings. This area also seems to be someplace to check luggage as evidenced by the rather nifty conveyor belt that comes in a full part. The moving parts of the set include a revolving door (a very tall one, for the first floor) that leads from the secure area of the airport out to the tarmac, and of course the conveyor belt.
Even in terms of play value it mostly seems to be a trade-off — 60104 loses the vending machine, cafe, baggage x-ray scanner, and a few seats on the plane but gains a baggage conveyor, a restroom, a refueling tank for the plane, an additional minifigure, and more seats in the waiting area. It's pretty nice to see the value of a LEGO air terminal remain fairly stable even though the price has not increased.
Basically, the only thing that the two sets have in common is that they both have planes. However there is quite a bit of difference on the inside of the planes. There are a lot more details in the Friends plane. In addition to the seats, there is a rolling service cart complete with refreshments, emergency lighting as well as a larger galley and lav in the back of the plane.
Since around 2000, the Lego Group has been promoting "Lego Serious Play", a form of business consultancy fostering creative thinking, in which team members build metaphors of their organizational identities and experiences using Lego bricks. Participants work through imaginary scenarios using visual three-dimensional Lego constructions, imaginatively exploring possibilities in a serious form of play.