1- Storing a single account balance is more memory efficient than storing a combination of UTXOs that make up a user’s balance. The benefit of having more space with the account model is that txns are completed way more efficiently and it allows new nodes to sync faster with the network because less data is required to be stored.
2- The account model is not as great as the UTXO model for privacy because txns on the account model are very simple. There is no notion of sending change back from/to one’s self as is the case in UTXO because txns in account model must send the exact amount to cover the txn and no more. So from the outside, anyone can observe to what addresses the txns are being sent and how much is being sent. Whereas in UTXO model, it is impossible to decipher to which accounts the txn outputs are going.