Bears' noses are hundreds of times better than canine noses, actually. In the nose department, bigger is better.
As agility goes, you are comparing apples to oranges. Seriously.
Canine muscle and feline muscle are designed in completely different ways. Cat muscle is designed to react instantly, almost reflexively, to the tiniest stimulus, with immense power. It expends all its energy all at once, so the cat has almost zero endurance over a long time.
Dog muscle is designed to be quick and strong, but most of all, it retains the maximum possible energy. It is made for long-term efficiency, to give the dog optimum stamina. It isn't as powerful or fast as a cat, pound for pound, but it CAN outlast the cat...if it survives long enough.