The legal framework for trusts is much more elaborate than for custodial accounts. Generally speaking, trusts are more expensive, complicated and time-consuming than custodial accounts. There are good reasons to use trusts in many situations, however. Trusts provide greater protections and more flexibility. Generally you should think of using a trust when you expect to transfer tens of thousands of dollars.
Custodial accounts are more suitable for smaller transfers.
A transfer to a child under UTMA or UGMA requires the involvement of a custodian . This is an adult who will manage the property until the child reaches the age when control passes to the child. The person transferring property to the child can act as custodian or name another adult to act in that capacity. The custodian manages the property, making decisions concerning buying and selling, reinvesting earnings and so forth. The custodian may also take money from the account to spend for the benefit of the child.