They're the hard-shell gourds. Luffas are sponge gourds. Many gourds get their common names from their shapes. However, the shape, color and wartiness depend on many factors that gardeners have little control over. First, weather factors such as rainfall and temperature affect the gourd's characteristics.
Gourds also have many genetic variations.
Even gourds on the same vine may not be the same size, shape and color. Usually, color is the most variable among the traits. But due to genetic instability, you can usually expect a variety of gourds in your garden. Saving seed from your crop won't likely yield the same type of gourds you had this season, since cross-pollination will usually occur between plants. The hard-shell types may benefit from some hand pollination.