Checkboard,
The massive loss of TAS when a high performance twin piston, eg C414AW, loses an engine and descends from F230-F250 to F120 means that much more fuel is required to cover this case if over remote areas like the sea with no close alternates. We're talking 230Kts TAS to about 175Kts TAS. Similarly with a decompression, you still lose the TAS though not as much coz you can still make 155Kts IAS, say 185Kts TAS.