Well, honestly shorter is better for buttons that bonk. If the cieling is high, then they get momentum and thats' when the damage happens. 1' to 2' is what I do...but even 2' can kill a spazzy bonker.
Coturnix quail aren't as bonky (esp adults), I have all my birds for the winter ina large rabbit hutch...it easily houses 30+ birds (not by square foot per bird standard but they can all stretch out, runaround, play etc and theres still a large amount of space empty.
Then i have a 6 hole pen built for fur animals, then was given to my friend who breeds rabbits and she sold it to me this summer. Each hole is 2ft by 2ft by 2ft tall. I can house 1 male and up to 5 hens in there fine---but it's more appropriate to put only 3 in there according to what others reccomend but i've had 6 birds total in the pens and they had all the room in the world. The buttons do crappy in it though as they freak and bonk their heads. Which is why i mention 1' for htem...my buttons do great in 1ft heighted pens, esp with the added 1inch craft foam padding the top. 
I also clip wings..but its' amazing how high they can jump JUST with legs alone....4ft i've witnessed...thtas' without flying feathers.
Use your imagination for coturnix, and go with your gut on how many per cage looks fine for you. If the birds arent cramped and they get along that's my motto. Mean birds aren't kept so any aggressors are culled and you'll get those in both species (buttons and coturnix)...its up to you what ya do with them no ones twisting yoru arm there
You can see my hutch and pens on my sig below where i have a thing typed up on coturnix care, breeding, genetics, raising etc.
