The difference between comparative and superlative

We use the comparative to compare one person, thing, action, event or group with another person, thing etc. We use the superlative to compare somebody/something with the whole group that she/he/it belongs to.

·         Mary is taller than her three sisters.

·         Mary is the tallest of the four girls.

·         He plays better than anybody else in the team.

·         He is the best player in the team.

·         Iron is more useful than any other metal.

·         Iron is the most useful metal.

When a group only has two members, we sometimes use the comparative instead of the superlative.

·         John and Tom are clever boys, but I think John is the cleverer/cleverest of the two.

·         Take the shorter/shortest of the two routes.

·         Alice and Mary are rich women. But Alice is the richer/richest of the two.

Some people feel that a superlative is incorrect in this case.