what do you use wallet or exchange for? Do you want to trade or hold ?
If you hold on a mid term or trade, you should use exchange. And hold your coin for security, you should use hardware wallet.
I prefer to use the exchange to keep his Altcoin. If you follow Altcoin in thick portfolios or websites like coinbase, it's inconvenient when you need to transfer them to the exchange before you want to make a buy-sell so keeping them on the trade will make it easy for you to create a buy-sell.