I'm going to say Belgium Malinois for both categories. The amount of drive they have is bar none, when training them even in something so little as fetch, and you hold them until you say go, they often turn back around and bite the handler in excitement. Thresholds are met in seconds and an inexperienced owner is doomed. Very few Mali handlers have no bite scars. That being said, they learn rapidly and have the ability to do anything. They are known to jump through windows of homes and they often end up in rescue because they require at least 2 hours daily of rigorous exercise.
For my wife and I together, the Corso has been extremely tough with her drive and rapid thresholds and strength. A better word is beastly, she is like having a beast around. Everything she does is very intense like a small monster, we always wondered why all of these working line breeders keep them outside in kennels (now we laughingly say oh that's why each time she has psycho zoomies or runs back and forth with a kong for 3 hours straight). We are both fighters and will not give up on any dog unless it attacks one of us.
Now she is going through the maturing stage and that is a whole new bag of worms, the potty training was the absolute worst possible, we have had to put one hallway off limits to her when not watching her, since doing so we have no pee at all. She is eager to please, high drive, willing to learn hard commands, great guarding skills, majestic when she heels she looks like she is doing a horse dance movement with her front legs, people always comment, she never pulled on the leash and while stubborn as all guard dogs should be, she listens to us.