OKEX is a good exchange and OKB could be a good coin to diversify your portfolio.
But OKB is in no way comparable to BNB, Okex has not been able to provide any more uses for OKB as of yet while BNB is already a popular payment coin even without the involvement of Binance.
Okex still has many ways to make you more profitable than Binance. However, at the moment, BNB is still better than OKB and I believe that both will develop together if the trend of investing in exchanged coins increases. Of course BNB will still be in the No. 1 position in this market and then will be coins like HT, OKB, KCS or BTMX because these are all exchange coins I know.