i think blockchain most trusted wallet so far, because You have full access to the private key. You can backup and store in the safest place, and don't worry lost your bitcoin.
By blockchain, are you referring to blockchain.info?
If so, please enlighten me about it since I haven't used it at all. I've only been introduced to Xapo from the first time I knew about bitcoin. Any specific advantage of blockchain over Xapo?
Well only Xapo owns the private keys, so you dont own the Bitcoins you have there, only some Xapo IOU. If nothing wrong happens, you can use your Xapo IOU and withdraw the Bitcoin. But the moment something goes wrong, you end up with just Xapo IOU, unable to withdraw the Bitcoin. Look at similar Bitfinex example what might happen at any time.
blockchain.info dont know the private keys in your wallet so its less risky to have Bitcoins there. But make sure you print out the recovery words for your wallet, because if you lose your login info, blockchain.info cannot recover your Bitcoins, because they dont know your private keys. So your expected to secure your login info/recovery words.
Xapo do not give you the private key and hence it is just like an exchange. If the site goes dead, all your coins are gone. So its better to use desktop wallet as then the funds will be in your control.