Had they met as 3-year-olds, champion trotters Moni Maker and Muscle Hill could have helped settle the debate as the greatest of them all. But since they raced a decade or so apart, it will be up to harness racing fans to decide who was better.

What started with a bracket of 32 world-renowned standardbreds comes down to Moni Maker versus Muscle Hill in the championship of the Greatest of All-Time Challenge. Fans can cast their final vote from Wednesday-Friday, May 6-8, via the Harness Racing FanZone twitter page. Voting will close Friday at 9 a.m. EST for the contest sponsored by Omega Alpha.

Moni Maker was a three-time Trotter of the Year in North America from 1998-2000 and went on to become an international star before she retired as the top-earning standardbred of all-time with $5.58 million in the bank and 67 wins in 105 starts. Muscle Hill was a two-time Breeders Crown winner in the late 2000s, Horse of the Year in the U.S. and Canada and $3.27 million earner with 20 wins in 21 starts -- all by one length or more. Both were inducted into the U.S. Harness Racing Hall of Fame a decade apart.

But it was their prowess at age 3 that launched both trotters toward super stardom. Moni Maker won 18 consecutive races as a sophomore and was named Trotting Mare of the Year. Muscle Hill, a $57,000 yearling purchase by Tom Pontone for trainer Greg Peck, was undefeated in 13 starts as a 3-year-old, including a 6-length win in the Hambletonian and a single-season record $2.46 million in earnings.

It didn’t end there. Moni Maker won 14 races and $2 million over the next two seasons, setting world records in Sweden’s Elitloppet and Denmark’s Copenhagen Cup. Muscle Hill was retired to stud, where his first seven foal crops produced 10 millionaires, making him the leading trotting sire four years running.

Their latest fete was advancing through the Greatest of All-Time Challenge semifinals. Moni Maker received 55.7 percent of the 228 votes cast to edge 1970s star Niatross (37-for-39, $2 million), winner of the 1980 Meadowlands Pace, the sport’s first $1 million race. Muscle Hill edged Mack Lobell, a two-time Breeders Crown winner and the best horse Hall of Famer John Campbell said he ever drove.