There are two ways to get coverage on a child, and they're built for different jobs. A child rider is an add-on that attaches to a parent's policy. A separate policy is a contract of its own, with the child as the insured person.
The rider covers all your children under a single cost, usually priced per thousand dollars of coverage. Face amounts typically run from $5,000 to $25,000, and the coverage lasts until the child hits an age in the low to mid twenties. Children born after you add it are covered automatically, with no new application. For a household with four kids, that's one cost covering four lives, and the price is small enough that the decision doesn't need a spreadsheet.
The most useful thing the rider does isn't the death benefit. It's the right to convert the rider into a permanent policy later. Most child riders let you trade the rider for a permanent policy later. You get some multiple of the rider's face amount, often five times, with no evidence of insurability. Evidence of insurability means proof the child is healthy enough to insure, so no evidence means no exam and no health questions. A $25,000 rider becomes a $125,000 permanent policy at 25, no matter what the medical history looks like by then. For a kid who develops type 1 diabetes at 14, that right is the difference between insurable and not.
A separate policy does something the rider can't. It builds cash value from the first premium. It locks in insurability permanently rather than for a conversion window. And it can be built with paid-up additions, which means extra coverage bought with dividends. By the time the child is 25 there's a real pot of money sitting there. Its face amount isn't capped at a multiple of a rider either. What that actually buys is in what a policy on your kid is actually buying.
The cost difference is where this gets decided. A rider covering four kids might run a few hundred dollars a year. A funded whole life policy on one child, built for cash value, is a real premium and a commitment for years. So the question isn't which one is better. It's what you're trying to buy.
If you want protection plus a guaranteed right to convert, for very little money, the rider does that and there's no reason to buy anything else. If you want an asset the child takes over as an adult, with cash value they can borrow against for a car or a down payment, the rider does none of that. A separate policy is the only version that gets you there.
Plenty of families do both, and it's the sensible answer when the kids are spread out in age. Fund a policy on each child you can afford. Then add the rider on the parent's policy to cover the ones still coming, and to hold the conversion right in reserve. Grandparents can carry part of the cost, which is covered in grandparents, you can start the policy yourself.
One trade-off on the rider that people don't discover until it matters. It lives on the parent's policy. If the parent lets that policy lapse or cashes it in, the rider goes with it. The coverage on the kids ends, and the conversion right ends with it. A separate policy on the child doesn't care what the parent does. So if the plan is for the child to eventually own this thing, handing them a contract is cleaner than handing them a deadline. The mechanics of that handoff are in let your teenager take the first loan against their own policy.