Modern carbon frames are designed with structural integrity in mind, the frame-building process allows more fine-tuning than aluminum. Aluminum's best quality is it's value, you can wreck one and buy another and still have spent less than a low-grade CF frame.
Not quite. Carbon fiber is a composite. Structural integrity is not one dimensional, and while carbon fiber frames are great in their intended loads, they are bad in puncture and abrasion, and that is inherent to carbon fiber.
It is so much easier to wreck a carbon fiber frame than an alu frame. It just takes one pointy rock or one bad slide. Whereas an alu frame will only receive cosmetic damage
