With Jaxx you have full control over your keys too
Except the keys aren't encrypted and anyone who gets access to your device can easily get your backup phrase. (Over a network not just physical access.)
Even when your Jaxx has a security PIN configured, anyone with 20 seconds of (network) access to your PC can extract your 12 word backup phrase and copy it down. Jaxx does not have to be running for this to happen.
With the 12 word backup phrase, they can later restore your wallet, including all of your private keys, on their own computers, and then proceed to transfer away all of your cryptocurrency.