I find there is very little consistancy with onions.
I have bought wonderful white "cooking onions" before.
They cook great and you can use them raw too.
The trouble is that onions keep very well, and I am sure I have been buying the same source stock for months.
Gradually the quality degenerates.
The red onions, which I see in asian shops too, look really good, and can taste great.
They are always about twice the price of ordinairy onions.
The same rule applies to them.
You get good and bad.
Having a quality onion is all that counts.
The only difference then, can be strength and sweetness
For making a quantity, the price definitely rules out red onions.