When to use Genitive in comparatives?

Question

So we can use either Genitive or чем when making comparisons. My question is, when should I prefer one over the other?Я круче его. Я круче, чем он. Я знаю это лучше тебя.Я знаю это лучше, чем ты. Она красивее той девушкой.Она более Красивая, чем та девушка.What are some general rules?)) Or your opinions?

Answer 1

You van express a comparison either with genitive case, or with the conjunction чем meaning "than" with no difference in meaning. This is more of a stylistical preference. Она красивее той девушки sounds more natural. A similar set of questions would arise when you discuss the usage of the superlative degree of camparison of adjectives, like самый красивый vs. красивейший. Here, as well, the difference would be more of a stylistical nature.

Answer 2

No difference in the meaning, but generally you should shoot for a simpler construct, which would be genitive. But use it correctly: your example bears a mistake. Она красивее той девушкИ.