"that of / those of" is very formal and necessary only in formal writing. 1 My dog's bark is cuter than that of yours. OK BUT TOO FORMAL Can I say "My dog's bark is cuter than yours? YES. NORMAL OPTION. 2 The salary of a professor is higher than that of a secretary. FORMAL. COULD BE OK IN CONTEXT. Can I say "The salary of a professor is higher than a secretary'S? NOTE THE ADDITIONAL 'S 3 The population of China is larger than that of Japan GOOD. "The population of China is larger than Japan'S. GOOD. NOTE 'S 4 The cost of eating out in New York is much more expensive than it is in Tokyo. GOOD. FORMAL. The cost of eating out in New York is much more expensive than in Tokyo? GOOD. LESS FORMAL. The grammar in 4 is different. We are not comparing two nouns that are possessed by people or places. So, we can't use "that/those of". We are comparing a situation in one place with a similar situation in another place.

Yes you are right, there are no difference between them