I can't comment on PS biz, which I know is a lot more comfy than standard business, but I've found redeyes in coach and business to be equally uncomfy. I've fly LAX-BOS on a 757 both in coach and business, and not really felt a difference. Albeit I cannot sleep without laying down flat, so that probably has something to do with!
I'm planning on upgrading on a flight to LAX soon so I can enjoy the longer time spent on the plane and a proper meal; everything seems kind of rushed on a late night flight so everyone can get to sleep.