Terror Mission (TFTD)
Big differences with Enemy Unknown are the introduction of 2 part terror missions. These tend to drain your ammo. PLUS, I think you have to actually pick up stuff from the first part to keep it (X-com agents too lazy to salvage it?)
I believe that the 2nd part is empty of civilians.
Both parts count towards your scoring, methinks.
Terror Missions ARE ON LAND. This is very bad, since most of your big guns early in the game only work underwater! Good luck taking out those heavily armored terror units using dart guns and grenades... Mag Ion Armor doesn't work here either.