For a native token on a Substrate chain you should use the Balances Pallet, not the Assets Pallet.
The balances pallet is specially optimized to minimize its computational and storage footprint. This means that when using the balances pallet, users will be paying the lowest possible fees and your chain will be using the least amount of weight per transaction.
Additionally, the Balances Pallet implements a number of core traits needed for a native token like
LockableCurrency, and supports things like vesting via the Vesting Pallet.