Big is a relative word and not always viewed the same way. In the case of Great Dane versus Irish wolfhound, the definition of big usually comes down to height or weight, leaving each a winner. Great Danes tend to be heavier while overall Irish wolfhounds tend to be taller.
What the Experts Say
The American Kennel Club official standards for recognized breeds is the bible of the dog world for owners of purebred dogs and generally considered the final judge. AKC official standards list 30 and 32 inches at the shoulder as the minimum acceptable height for females and males, respectively, for the Irish wolfhound, with an ideal maximum of 34 inches in height. Weight minimums are 105 pounds for females and 120 pounds for males. For the Great Dane, the AKC standard requires 28- and 30-inch height minimums for females and males, respectively, but suggests an ideal minimum of 30 and 32 inches and lists no maximum height. For weight, the AKC specifies no limits but calls only for a well-muscled appearance.
Big Means Tall
If being tall is the only requirement, then Great Danes win paws down for record-breaking height. Giant George was proclaimed on Feb. 15, 2010 by the Guinness Book of World Records to be both the tallest living dog and the world's tallest dog ever. A solid gray Great Dane male, he was measured at 43 inches at the shoulder. George died Oct. 17, 2013, but the current record holder keeps Great Danes on top for height. A Great Dane named Zeus, who stands 44 inches tall beat George by an inch in 2013 to become the tallest dog and the new tallest dog ever.
No, Big Means Heavy
If heavy stands for anything, Great Danes and Irish wolfhounds have nothing on the Guinness Book of World Records English mastiffs. The record-breakers are Zorba at 343 pounds, Moose at 291 pounds, Kell at 286 pounds and Hercules, who in 2001, claimed title to the heaviest living dog at that time -- 282 pounds. However, in the contest between Great Danes and Irish wolfhounds, the winner for weight goes to the Great Dane, since the average, healthy Great Dane outweighs the average healthy Irish wolfhound by about 30 pounds.
And the Winner Is...
Overall Great Danes tend to be heavier than Irish wolfhounds, who are on average the taller of the two breeds. Individual variation between any two dogs makes comparisons nearly impossible except as breed averages. Big, therefore, is a relative term dependent entirely upon your definition.