Some will say that spices are all created equal: oregano is oregano, cinnamon is cinnamon. Some even have the same mindset with cooking oils being equal.
It's like Joel said, beer brands and varieties differ dramatically, the same holds true with spices.
The problem with store shelf spices is that you have no idea what variety of the spice, or what region it originated from.
Yes there is a difference in flavors between varieties, as well as the region of origin.
Lets take Cinnamon for an Example...
The difference between store cinnamon falls between two varieties, burmannii and cassia but they are never listed as such on the label (sometimes they are even blended). Then there is Ceylon cinnamon, which is slightly sweeter and more aromatic, is also available in some specialty retail markets. For the average consumer, it's much harder to find Ceylon cinnamon and Saigon cinnamon as well as the fact that they are much more expensive.
As with many other spices and products, each variety of cinnamon has a grade scale (A, B, and C). Most stores typically carry the lower grades (B or C), but Grade "A" can be purchased through specialty spice outlets.
Cinnamomum burmannii - Called Korintje cinnamon, Padang cinnamon, or Indonesian cinnamon; It has a sharp flavor with a slightly bitter edge. Indonesian cinnamon is by far the most common and the cheapest type of cinnamon sold in the US. It contains no eugenol, but has higher amounts of coumarin than cassia. It is grown on west coast of the island of Sumatra and Jambi province of Indonesia. It is a common choice for cheap commercial bakeries because it has a familiar flavor and a very low cost.
Cinnamomum cassia - Called cassia cinnamon, or Chinese cinnamon; It is grown in southern China, and southeastern Asia. Chinese cassia is used as a common flavoring agent for confectioneries, desserts, pastries, and meat. Commonly the only cinnamon sold in European countries, and it is simply labeled as "cassia".
Cinnamomum verum - Called Sri Lanka cinnamon or Ceylon cinnamon; Sweeter than cassia cinnamon, it also has a higher price because of it's quality. Sri Lanka alone still produces 80% of this variety, the remainder of the supply is commercially grown in Seychelles and Madagascar. Many artisanal bakers favor this variety of cinnamon because it is sweeter, more aromatic, a bit more subtle, and a more delicate taste than the cheaper varieties. Many claim Ceylon to be the "true" variety of cinnamon and some bakers refer to the other cheaper varieties are "fake".
Cinnamomum loureiroi - Called Saigon cinnamon or Vietnamese cinnamon; it has 1-5% essential oil in content, which is the highest of all the cinnamon species. It also has a more pronounced and complex aroma, so consequently it commands a higher price because of the demand for it's quality. Because of it's high price, pure Saigon cinnamon or Vietnamese cinnamon are mainly sold through specialty purveyors of fine spices.
Cinnamomum citriodorum - Called Malabar cinnamon, it has a characteristic smell of lemon grass. Once a highly prized type of cinnamon, which was harvested nearly to the edge of extinction. The World Conservation Monitoring Centr added Cinnamomum citriodorum to the list of "Threatened Species" in 1988.
Cinnamomum tamala - Called Indian bay leaf. Unlike other species of cinnamon where the bark is harvested from the plant; the leaves of this have a clove-like aroma with a hint of a vibrant "peppery" flavor. The leaves are used for culinary purposes for their flavoring. The bark is sometimes used for cooking, although it is regarded as inferior to the true cinnamon varieties listed above.
This is true of other spices as well.....
Just look at all the varieties of chili peppers, each imparting a different flavor (some completely different) with varying levels of heat.
