What's hops got to do with it?

In our first two recipes, Golden Amber Wheat (II), we chose to keep everything constant except for the hops. That way we would be able to understand what the hops really do to the beer. There wasn't any in depth reasoning for our choosing Centennial and Cascade hops for comparison, we just read some descriptions online and asked some friend's thoughts on what he uses.

I did some research and found this link (see below). Just so happens that Centennial and Cascade are listed as substitutes for one another...

Hops contain alpha and beta acids. Bittering hops have more alpha acids and aromatic hops have more beta acids, although hops are mainly measured in alpha acids (aromatic hops have alpha acids ~5%). Hops have 4 essential oils that aid in the aroma; sometimes brewers opt to add aroma hops after fermentation, to avoid boiling off the essential oils, in a process called "dry hopping".

Hops Profile Chart

Bullion-Bittering
Alpha Acid: 6.5-9% Beta Acid: 3.2-4.7%
Aroma: Intense, black currant aroma, spicy and pungent.
Storage: 40-50%
Used for: Mainly bittering. Stouts and Dark ales.
Substitutions: Northern Brewer and Galena.

Cascade- Finishing
Alpha Acid: 4.5-7% Beta Acid: 4.5-7%
Aroma: Pleasant, flowery and spicy, citrus-like.
Storage: 48-52%
Used For: Good for flavor and aroma, but an acceptable bittering hop. Ales and lagers.
Substitutions: Centennial

Centennial- Bittering
Alpha Acid: 9.5-11.5% Beta Acid: 3.5-4.5%
Aroma: Medium with floral and citrus tones.
Storage: 60-65%
Used For: Aromatic but acceptable for bittering. Medium to Dark American Ales.
Substitutions: Cascade

Challenger- All purpose
Alpha Acid: 7-10% Beta Acid: 4-4.5%
Aroma: Mild to Moderate, quite spicy.
Storage: 70-85%
Used For: Popular bittering hop used primarily in the UK. British ales and lagers
Substitutions: Undetermined

Chinook-Bittering
Alpha Acid: 12-14% Beta Acid: 3-4%
Aroma: Mild to medium-heavy, spicy, distinct piney aroma.
Storage: 60-70%
Used For: Strong bittering ability. All American lagers and ales.
Substitutions: Galena, Cluster, Nugget

Cluster- All Purpose
Alpha Acid: 5.5-8.5% Beta Acid: 4.5-5.5%
Aroma: floral
Storage: 80-85%
Used For: Bittering with good flavor. Light and dark American lagers.
Substitutions: Galena, Chinook.

Columbus- All Purpose
Alpha Acid: 14-16% Beta: 4.5-5.5%
Aroma: pleasant
Storage: under evaluation
Used For: Bittering mainly, good flavor.
Subs: Undetermined

Crystal- Finishing
Alpha: 2-4.5% Beta: 4.5-6.5%
Aroma: Mild and pleasant
Storage: 50%
Used For: Aroma
Substitutions: Liberty, Mt. Hood, German Hallertau

Eroica- All Purpose
Alpha Acid: 11-13% Beta Acid: 4-5.5%
Aroma: Quite strong but not unpleasant.
Storage: 55-65%
Used For: bittering and good aroma for high alpha hops (use sparingly). Pale ales, dark ales and Stouts
Substitutions: Chinook, Cluster, Galena, Nugget.

Fuggles- Finishing
Alpha Acid: 4-5.5% Beta Acid: 1.5-2%
Aroma: Mild and pleasant, spicy, soft, woody.
Storage: 60-65%
Used For: Finishing, Dry hopping. English ales, especially Pale ales, Porters, Stouts.
Substitutions: Willamette, East Kent Goldings, Styrian Goldings.

Galena- Bittering
Alpha Acid: 12-14% Beta Acid: 7-9%
Aroma: Medium but pleasant hoppiness.
Storage: 75-80%
Used For: Very bitter, but blends well with finishing hops. American ales and lagers. Suitable for all beer styles.
Substitutions: Nugget, Cluster, Chinook.

Hallertau- Finishing
Alpha: 4-6% Beta: 3.5-4.5%
Aroma: mild, pleasant and slightly flowery.
Storage: 45%
Used For: Good all around bittering and finishing. Stock ales, Altbiers, Belgian ales, and Continental style lagers.
Substitutions: Mt. Hood, Liberty, Crystal.

Hallertau- Finishing
Alpha: 3.5-5.5% Beta: 3-4%
Aroma: Mild to semi-strong, the most popular aroma variety.
Storage: 50-60%
Used For: Versatile bittering and finishing. Wheats, Altbiers, Pilseners, Belgian ales, American and German lagers.
Substitutions: Mt. Hood, Liberty, Crystal.

Kent Goldings- Finishing
Alpha Acid: 4-5.5% Beta Acid: 2-3.5%
Aroma: Gentle, Fragrant and pleasant
Storage: 65-80%
Used For: Classic English ales, kettle hopping, dry hopping, spicy flavor. Pale ales, Bitters, Porters, Stouts.
Substitutions: Goldings (British Columbia), Fuggles, Willamette.

Liberty- Finishing
Alpha Acid: 3-5% Beta Acid: 3-4%
Aroma: Mild and pleasant, quite fine.
Storage: 35-55%
Used For: Finishing. American and German ales and lagers.
Substitutions: German Hallertau, Mt. Hood, Crystal.

Mount Hood- Finishing
Alpha Acid: 5-8% Beta Acid: 5-7.5%
Aroma: Mild, pleasant, clean, light, and delicate.
Storage: 50-60%
Used For: Aroma and flavor. American and German ales and lagers.
Substitutions: German Hallertau, Liberty, Crystal.

Northern Brewer- All Purpose
Alpha Acid: 8-10% Beta Acid: 3-5%
Aroma: Medium-strong, woody with evergreen and mint overtones.
Storage: 70-80%
Used For: Good for bittering with strong flavors and very fragrant. Steam beers, Dark English ales, and German lagers.
Substitutions: Galena, Perle.

Nugget- All Purpose
Alpha Acid: 12-14% Beta Acid: 4-6%
Aroma: Quite heavy and herbal, spicy.
Storage: 70-80%
Used For: Extremely bitter. Medium to Dark ales and lagers.
Substitutions: Chinook, Galena, Cluster

Perle- All Purpose
Alpha Acid: 7-9.5% Beta Acid: 4-5%
Aroma: Pleasant, slightly spicy
Storage: 80-85%
Used For: Minty bittering and good "green hop" aromas. All non-pilsener lagers, wheats
Substitutions: Northern Brewer, Cluster, Galena

Pride of Ringwood- All Purpose
Alpha Acid: 7-10% Beta Acid: 5.3-6.5%
Aroma: Quite pronounced but not unpleasant, citrus-like.
Storage: 45-55%
Used For: Finishing, very flavorful. Pilseners, Continental
Used For: Disregard above. Predominantly bittering but with interesting aromatic qualities. British ales, Australian-style ales and lagers.
Substitutions: Centennial, Galena, Cluster

Saaz (U.S.A)- Finishing
Alpha Acid: 3-4.5% Beta Acid: 3-4.5%
Aroma: Very mild and pleasant, spicy and fragrant
Storage: 45-55%
Used For: Finishing, very flavorful. Pilseners, Continental lagers and Wheats.
Substitutions: Czech Saaz

Saaz- (Czechoslovakia) -Finishing
Alpha Acid: 3-4.5% Beta Acid: 3-4.5%
Aroma: Very mild with pleasant hoppy notes.
Storage: 45-55%
Used For: Finishing. Bohemian-style beers, Continental lagers, Wheats, Pilsener lagers.
Substitutions: Tettnang, U.S. Saaz

Styrian Goldings- Finishing

Alpha Acid: 4.5-6% Beta Acid: 2-3%
Aroma: Delicate, slightly spicy, soft and floral.
Storage: 65-80%
Used For: Bittering, finishing, dry hopping. English style ales, Vienna/Oktoberfest lagers, Belgian ales, Pilseners.
Substitutions: Fuggles, Willamette.

Target-All Purpose

Alpha Acid: 9.5-12.5% Beta Acid: 5-5.5%
Aroma: Pleasant English hop aroma, quite intense.
Storage: 45-55%
Used For: Robust bittering. British ales and lagers.
Substitutions: East Kent Goldings.

Tettnang- Finishing
Alpha Acid: 4-5% Beta Acid: 3-4%
Aroma: Fine, very spicy, mild, floral, very aromatic.
Storage: 55-60%
Used For: Finishing. Wheats and lagers.
Substitutions: Saaz

Willamette- Finishing
Alpha Acid: 4-6% Beta Acid: 3-4%
Aroma: mild and pleasant, slightly spicy, aromatic.
Storage: 60-65%
Used For: Finishing, dry hopping. American and British ales.
Substitutions: Fuggles, Styrian Goldings, Kent Goldings.