BTC is used like gold, sparingly, with high transaction costs and low # of transactions mostly of large $ size.
I believe that in the long term, it won't work out. If BCH actually gets used for day-to-day purchases and if BCH starts getting a prominent place on the exchanges, the value will increase, and once the value of BCH raises above the BTC value, then we don't really need BTC anymore.
I may of course be wrong. The thing that one actually can validate all transactions using commodity hardware, and even listen to sattellite broadcasts of the blockchain ... it's for sure some value in that.
Anyway, security-wise - the hash power follows the coin value, if BCH would be more valued then it would get the majority of the hashing power. With a falling difficulty on BTC, and with some few actors controlling wast amounts of mining hardware, people may be worried about the security.