I perform car seat checks at a local fire department every month, and I almost always get asked about how safe a particular car seat is. I will tell you, as long as a car seat is installed properly, it is safe. All car seat manufacturers have to meet the same federal requirements- so any car seat that you buy from a legitimate retailer has been tested and meets the federal requirements and therefore is deemed safe. But again- it has to be installed properly AND the child has to properly fit and be properly harnessed in the car seat.
When choosing a car seat, it is best to buy the car seat that will fit in your vehicle, fits in your budget, and fits your child. The next important step is to ensure it is installed properly! If you are not sure, there are CPST's like me all over the United States that can check the installation of your kid's car seat.
Safe Kids Worldwide is the organization that I am certified by as a Child Passenger Safety Technician.
reach out to me- I can help you find a technician near you or answer questions firstname.lastname@example.org