Mike goes after people who rarely see him coming and whom he can tailor his plans towards without their knowledge. Most people he's operating against have no idea he's working against them until it's too late, and even then their ability to respond is limited by their lack of knowledge regarding his ability. He's an x-factor who can fight their fire with water.
In contrast, Oracle often has less information and due to the nature of her team, less of an advantage as Black Canary is far from an unknown and she's facing people who can equal or surpass her ability to bring force. Add in metahumans, and Oracle's use of information has to differ.
Or, to put it another way, Mike's situation allows him to burn someone down to the ground and salt the earth,. rendering his enemy a non threat for all time. All Oracle can get is information about Achilles' heel and trust that Canary can hit it.