PHILADELPHIA - So, the filly or the mare?\nWhat if Rachel Alexandra and Zenyatta end up in a starting gate together?\nI have two West Coast friends who are convinced. One is sure Rachel would win. The other is equally certain Zenyatta would win.\nMe? I am not so sure.\nComparisons are fascinating, if ultimately futile. They give us hints, but there is only one way to know.\nThe running styles of the 3-year-old and 5-year-old could not be more different. So, one would think that would give the speedy Rachel an edge. But if the race is on an artificial surface, that speed may not be an edge at all.\nMidway through her 3-year-old season, Rachel has raced 11 times, one more start than the 5-year-old Zenyatta has in her career. Zenyatta did not make her debut until November of her 3-year-old season, about the same time Jess Jackson and company may be announcing Rachel's retirement.\nWe know Rachel can lose. We can't be so sure about the unbeaten Zenyatta.\nBut how sure are we that Rachel can lose with Calvin Borel? After all, the jockey is 6 for 6 with the filly, including that overwhelming win in the Kentucky Oaks and the dazzling win in the Preakness.\nRachel has posted five consecutive triple-digit Beyer Speed Figures during her wonderful 2009 season. Zenyatta has six career triple-digit Beyers.\nA reasonable case could be made that since Rachel is getting all those big Beyers as a 3-year-old, her Beyer ceiling could be higher. In fact, she has posted two consecutive 108 Beyers, serious business for a 3-year-old filly in the spring.\nZenyatta posted two consecutive 108 Beyers late last summer and in early fall. So, we know she can get to the number.\nAs a true Beyer disciple, I should probably lean toward Rachel. She has that gliding stride that suggests she can go higher on the Beyer scale.\nHowever, I admit to having reservations about the Beyers as they relate to Zenyatta. The mare only runs for part of each race, the part where she effortlessly rolls by all the horses in front of her and wins comfortably.\nI have never been a big believer in the old "good horses run only as fast as they have to" theory. Horses, good or bad, generally run as fast as they can.\nZenyatta may be the exception to the rule. She actually makes you smile when you watch her run as she hangs out at the back of the pack and then runs by horses so fast on the turn that the others quickly turn invisible. It is some scene and it repeats itself race after race.\nIt is unknown if Rachel is going to run in the Belmont Stakes. If she does, I would like her to beat the boys again. She would have such a running-style edge that it would be difficult to pick against her. Whatever the decision, we already know she can beat the boys.\nGiven the pace pressure in the Preakness, Rachel ran a dominating race. Mine That Bird was really rolling late, but I am not convinced the Kentucky Derby winner would have ever gone by. During the gallop out, the filly took off again when the Derby winner got right next to her after the wire.\nWe don't know if Zenyatta can beat the boys. In fact, Zenyatta is still a bit of a mystery because she did not race early in her 3-year-old season and has only raced outside the artificial world of Southern California one time.\nZenyatta was awesome when she crushed Ginger Punch in the 2008 Apple Blossom at Oaklawn Park, but it would be nice to see her in New York or at Delaware Park for the $1omillion Delaware Handicap this summer. However, traveling apparently is not in the cards, as a repeat schedule of Vanity (Hollywood Park), Clement Hirsch (Del Mar), Lady's Secret (Santa Anita), and Breeders' Cup Ladies' Classic (Santa Anita) appears most likely for Zenyatta.\nI am not sure what any of that would prove. Or maybe Zenyatta has nothing to prove. All she does is win every time she runs. Still, a risk akin to Rachel's Preakness might be in order at some point during the season.\nSo, the filly or the mare?\nIn a match race, the filly. In a race with a hotly contested pace, the mare. In a race where multiple race-shape scenarios could be imagined, I want to see it.