one与that虽可用来指代同名异物, 但one为泛指, 相当于a/an+名词; that为特指, 相当于the +名词.所以one所指代的名词的修饰语一般为 a/an /some /any; that所指代的名词的修饰语往往是the /this /that.
A chair made of steel is stronger than one made of wood. (该句中one可以换成a chair)
The water in the cup is hotter than that in the pot. (该句中that可以换成 the water)
one只能取代可数名词, 取代可数名词复数时用ones; that既可以取代不可数名词也可以取代可数名词, 取代可数名词复数时用 those.
There were a few young people and some older ones in the house. (ones取代可数名词复数people)
The weather of Guangzhou is hotter than that of Beijing . (that取代不可数名词 weather)
These pictures are more beautiful than those. (those取代可数名词复数 pictures)