From my point of view the best wallet to hold alt coins is hardware wallet because hardware is very secure so you all should use hardware wallet if you want to hold any token for long term but many of us can't buy hardware wallet they even use Metamask and Trust wallet Both are safe for my opinion.
As a trader, I didn't even use a hardware wallet and so far I didn't get hacked or lost my assets it really depends on the user on how they can keep and secure their assets on a wallet. I keep my assets on known exchange and Metamask since I am using them since the beginning of trading and keeping my altcoins.
Keeping an asset on a secure exchange can be taken advantage of, In case of a sudden up or drop in the market, you can execute a trade quickly.