Super Hunt is right, I used stupid in place of inflexible and stubborn. I've found generally that the females of most breeds to be easier to train and more eager to please.
Got to know the dog of a girlfriend of my youngest daughter over Thanksgiving. Half Ridgeback and half Beagle, interesting mix. She seemed eager to please and trainable. When I let her out in the large yard she worked it like a pro, her nose went to the ground and she investigated every corner of that yard. When somebody came late to the party, she would *advance* she is basically brave, not overly timid and she has a bark twice the size of her body. That Ridgeback guard dog thing is strong in her.
I had a Boxer Shepard mix, she was prone to be a herding dog, but I could train her to do anything. If I could communicate to her what I wanted she would do it.
The trouble with mixes is you never really know how the genes are going to present and which instincts are going to be dominant. With pure breeds you can largely predict which instincts are going to be dominant.
Talking about instincts, my last Weimaraner was nose dominant, a born pointer. But stuck way back in those genes someplace was a strong owner protection gene and guard dog gene. Twice he saved my bacon by coming out of the dark to threaten somebody who meant me harm. Pure instinct, I never trained him to it, he was generally kind of a bone head, but was a good gun dog and had his surprise uses.