How We Roll Winner
Actually, there's a finer catch to descriptions and dialogue. They are both highly situation sensitive.
For example, you are being chased on a busy street where there are lot of people around, the shops are bustling and you are running towards a deserted part of the city. If your pursuer is a trained assassin who is holding a chainsaw in his hand and is merely half a metre behind you, there is absolutely no way that you are supposed to get down to describing the streets and the shops. You'd rather describe the duration it'll take for your heart to explode with fear.
So that's one factor. Of course, the finer points are the nature of the pursuer, the weapon he's wielding and his distance from you.
Usually, authors don't venture that deep into the works opting to go for the general situation, the reason being it affects the Pacing of the story greatly. I won't go into deep here seeing as I am not a qualified literature teacher, nor am I a celebrated author, not yet at least.^^
Anyways, dialogues follow the same procedure. Take the same situation as I took above only that this time, there's two of you.
Assassin's Distance from you: 2 feet
You: Help...!!! No..!!! Help...!!
Assassin's distance from you: 1 metre
You to your brother: Faster...!!! Run faster...!!
Assassin's distance from you: A quarter mile
You to your brother: He's coming..! Hide somewhere.
Assassin's distance from you: 1 mile
You to your brother: Hey, he has a chainsaw. He's running at us. Go, go go. Run...!!
So you see, Distance is directly proportional to dialogue length. Again weapons, nature of pursuer are all factors, and in case of dialogues, play a more significant role than in case of Description.
So there, I am really putting myself in deep waters posting this here. I hope it helps readers.^^
Again, I am NOT an English teacher, nor am I a famous author. The information I've provided above is purely my own experience that I am sharing and should in no way be considered anything more, especially not a guide, unofficial or official.