This will all depend on your budget, what function you want out of your car seat, and whether you want multi-purpose vessels. Many rear-facing car seats, for example, also function as carriers for newborns, but you’d be hard-pressed to find this functionality in a two-stage car seat. Additionally, it will be more expensive to buy a seat for each stage of your child’s growth, but, as they say, sometimes a master of one is better than a master of none. A car seat that’s meant to serve only one function may be safer or more accessible than a car seat that’s been designed to do multiple things.