I make use of both: online wallets that work as exchanges too and Windows or Android apps like MyCrypto. It all depends on the kind of use. I mostly need online wallets to quickly receive and quickly transfer my cryptocurrencies to my local exchange to be converted to FIAT. I use apps like MyCrypto to store cryptocurrencies for long and very long periods. Until now I haven't purchased a Trezor or similar because my cryptocurrencies amounts are not worth the expense.