The miniature railway is actually a faster mode of transport as opposed to a chairlift, but it is still slower than the monorail.
The American Style Steam Trains support less cars than the Steam Trains or Steam Trains with Covered Cars.
Trivia
In Roller Coaster Tycoon 1 & 2, the Miniature Railroad could only operate in a circuit, but in Roller Coaster Tycoon 3, it could operate in shuttle mode.
The standard trains in Roller Coaster Tycoon 1 & 2 are based off those of the Ravenglass & Eskdale Railway, a miniature railway in Britain and the "American" styled ones in all games are based off old American steam locomotives that operated in the 1800's.