I use Blockchain and Coinbase and I never had a problem ever since I started using those 2. I downloaded Armory a month ago but I cant get it running so I give up on it and continue using Blockchain and Coinbase. You just need to know how to protect your coins like using 2fa and don't just rely on what the site offers as protection.
I also using both coinbase and xapo, and there is no problem since first time i use it untill now everything is going okay..the main problem i prefer using online wallet is that i have problem to download full blockchain if i use desktop wallet