In theory, an un-neutered male is best. Their marking and urine odor says "everything beyond this smell is MINE". They also tend to protect a much larger perimeter. Females are more apt to attract if not spayed, won't urine mark their property lines, just don't want predators near what they feel they need to protect.
The only problem with a male would be if a female coyote is in heat she could "distract" him away and then if they are packing up like they sometime do up here you could end up with a dead dog. Farmers/ranchers have actually lost yearling calves to coyote packs here in north Dakota.