What is the difference between merlot and shiraz? Both in thickness and taste?

Answer 1

Here's a short version: Merlot is known as an 'entry level' red wine for beginning red wine crossovers from white.
Shiraz is a much fuller bodied wine with more body or 'thickness' and has more mature taste.
Why don't you buy a half-way decent bottle of each and taste them both?

.

Answer 2

Merlot is a red wine grape that is used as both a blending grape and for varietal wines. Merlot-based wines usually have medium body with hints of berry, plum, and currant. Its softness and "fleshiness", combined with its earlier ripening, makes Merlot an ideal grape to blend with the sterner, later-ripening Cabernet Sauvignon. This flexibility has helped to make it one of the most popular red wine varietals in the United States.[1]

Shiraz or Syrah is a variety of grape used in wine. The names are interchangeable. It is called Syrah in France and most often in the United States, South Africa, Australia, and Canada it is known as Shiraz. In Australia it used to be called Hermitage up to the late 1980s. It should not be confused with Petite Sirah, a synonym for Durif, which is a different type of grape. Its name stems from Shiraz--the city of flowers, wine and poetry in Persia/Iran--in the heart of an ancient winemaking region. The grape also has many other synonyms that are used in various parts of the world including Antourenein Noir, Balsamina, Candive, Entournerein, Hignin Noir, Marsanne Noir, Schiras, Sirac, Syra, Syrac, Serine, and Sereine.[1]

Answer 3

To my uneducated palate, merlot seems mellower and more fruity, and less viscous, less "thick." Shiraz seems more grapey and has more bite, sort of like zinfandel.