Jaxx is insecure? I've heard about it a lot but never actually used it, although this is the first time I've heard it's insecure. Anyway, since android phones run apps in a VM a mobile wallet on an android phone is the most secure type of wallet short of a cold wallet (if you use IPhone then I can't really help you there).
It is insecure because they don't store your seed safely. This means that anyone with access to your device can steal all your coins without any problem. The worst part: Their devs are saying they won't fix those issues because they are "very comfortable with this security model for hotwallets" and they expect the user to "maintain control of their devices and keep them away from anyone that may steal your wallet".
Not only this, but their wallet have a lot of bugs unfixed and you may end up losing your coins. Just check the tons of issues the users are experiencing in Jaxx's subreddit /r/jaxx/
On the other side, people may be overreacting.
https://medium.com/@homakov/why-you-shouldnt-worry-about-the-jaxx-hack-6344a4c4a11