Taking CryptoKitties as example, I'm sure it's possible to achieve the same concept of Crypto Collectable creating new kitties as Smart Contracts instead of using Tokens. Which would be the consequences of doing so? I'm looking for a technical anwser :)
Well, tokens are smart contracts.
All tokens are based on a smart contract - there can be no tokens without a smart contract. For example an ERC20 token is simply a standard which defines how a smart contract stores a ledger of token owners. So the contract itself basically contains information about which address owns how many of its tokens and some functionality to transfer the tokens around.
Furthermore, when you want to "send" tokens from address A to address B you can't send them like you send Ether. A transactions can't include tokens explicitly. Instead, when you are sending tokens, you are actually interacting with the token's smart contract and telling it to change its internal ledger to assign your tokens to another address. So tokens are not explicitly sent, they are always only reassigned inside the token contract.
as Smart Contracts instead of using Tokens
As Laurie points out, this is not really a choice. It's all smart contracts.
ERC721 is a standard interface. The advantage is interoperability with other contracts and wallets that understand the contract you wrote about the assets your contract's ledger represents.
Hope it helps.