Two classy fillies had the better of their male counterparts in the Caulfield Classic on Saturday.

Robert Smerdon had the option of running stablemates Fontein Ruby and Crafty in the Ethereal Stakes for three-year-old fillies over the same trip but elected for the better prizemoney in the Caulfield Classic.

Ridden by Mark Zahra, Fontein Ruby ($13) showed her fighting qualities to hold off the Craig Williams ridden Crafty ($6) to score by a neck with Firehouse Rock ($51) three-quarters-of-a-length away third.

With the Caulfield Classic having $630,000 more in prizemoney than the Ethereal, Smerdon elected to run his two fillies against the boys.

And with the rise in trip from 1600m to 2000m, Smerdon expected Crafty to be the better stayer.

But Fontein Ruby showed she is all heart as she first of all fought off Firehouse Rock, which Zahra said said had headed him in the straight, and then held off a late challenge from Crafty.

Smerdon said Fontein Ruby was now likely to head to the Wakeful Stakes (2000m) at Flemington on November 1 and then onto the Crown Oaks (2500m) while Crafty was likely to head straight to the Oaks.

"The fillies against the colts, they've done a good job," Smerdon said.

"Fair to say we would have run both in the fillies race but for the generosity of the MRC.

"The prizemoney is outstanding."

Smerdon said Fontein Ruby doesn't have the pedigree to run much further than 1600m, but said what she does have is a great constitution.

He also said a lot of Derby and Oaks winners over the years don't necessarily have the pedigree to be winners at 2500m, but get there on their class.

"As we know over time that a lot of horses win Derby's and Oaks's that aren't genuine stayers," Smerdon said.

"I think (Smerdon-trained) Mosheen was a miler essentially but she won an Oaks."

Even Zahra doubted Fontein Ruby could run out a strong 2000m, but got a great kick out of her win.

"Because I've had such an association with her the win is quite special," Zahra said.

"I love her attitude. She's a bit of a tart in the mornings but she puts a lot of aggression into her races and that's why she's a good horse."