In general there are three basic types of onions in the American Market, the Bermuda-Granex-Grano Type , which are flat to top shaped, mild, and early maturing, Late Crop Onions, mostly globes, with yellow, white, or red skins, and mild flavor, and a creole top  and other Very Strong Flavored Onions, example - Australian Brown, Ebenezer and White Portugal. 

Pungency is not always related to variety as the same variety grown in different locations and in different soils may have a different flavor.