I'm from onion growing country and what I've learned in Mexico is that the brown skinned or what we called dry onions are cooking onions because they have more flavor. The while onions are used generally raw because they are milder; same with red onions. Sometimes the white onions can be eaten like an apple (similar to a Vidalia). But white and red onions are not consistent in flavor. If they are older they are generally hotter, ie, more flavor. It's a crap shoot when you buy them.