Is there a difference in ability or trainability between males and females?
The gender gap in labs regarding trainability is very small. The important factor is their position in the pecking order of the litter. Example: the Alpha dog, regardless of gender, will be the most difficult dog in the litter to train. There is no discernable difference in companionship, hunting ability, or trainability between the genders. I would give the edge to the males in endurance.
