While there are a couple of benefits of collision insurance, the main one is that you can file a claim and receive reimbursement regardless of who was at fault. Collision claims usually get processed faster than property damage claims because the insurance company does not have to spend time investigating who was at-fault. Another benefit is that you only deal with your own insurance company, rather than another insurer with less incentive to pay for your claim. Collision insurance can also be used toward your rental car in most cases, which can spare you from having to buy rental car insurance.
Comprehensive insurance is a coverage that helps pay to replace or repair your vehicle if it's stolen or damaged in an incident that's not a collision. Comprehensive typically covers damage from fire, vandalism or falling objects (like a tree or hail). If you're financing or leasing your car, your lender likely requires comprehensive coverage. If you own your vehicle outright, it's an optional coverage on your car insurance policy.