If you are making a bracket that is going to provide a reasonable level of support, it probably should not be stressed at close to yield strength, since the deflection may be high. Elastic deflection is a function of Young's modulus and section properties, not strength. I vote for good section properties produced by using thicker material; not higher strength material.
What type of tooling is the proposed part going to be produced on? Open setup with press brake, or a dedicated forming die with trimming operations afterward? If you are making parts on a press brake, the formability is probably not going to be an issue, unless there are constraints that you haven't mentioned yet.