They're both correct but have different meanings: They have a good sense of smell means that their ability to smell things is really good They have good noses means literally that their noses are nice I think you meant to say the first one though haha

They are both correct and mean the same thing. Normally, we say a dog has a good sense of smell. However, since he smells with his nose, we also can say "he has a good nose". This does NOT mean he has a "pretty" nose. It means he has a nose with a GOOD sense of smell.

If two men where hunting with dogs, it's possible that one could be said to have: a good nose It's somewhat of a colloquialism but not entirely. They have good noses after all.

"Dogs have a good sense of smell" is perfectly correct and natural. "Dogs have a keen sense of smell" is more idiomatic. "Dogs have a good nose" isn't correct, for the reasons Rohan mentions. However, it would be understood, and in real life everyone would know that you meant that they have a good sense of smell.