mare vs gelding for endurance

["guest@endurance.net" <guest@endurance.net>]

tonya marx marxa@bellsouth.net
Hello.  I have been doing competitive trail, but am ready to move up to endurance.  I have found a super mare, lovely gaits, and good bone and attitude.  My worry is that it seems most top endurance finishers are geldings, and should I steer clear of mares if I want to be a top contender in big rides such as Old Dominion or Tevis?  This is an Arab mare, marish when she is in season, but not bad; and she is not otherwise high strung or flighty or witchy.  She is a pretty low key Arab.  Any input is greatly appreciated!