If DRO means that dynamic range is optimized, what sense does dro bracketing make? Three images, 1 less than optimal, 2 optimal, 3 more than optimal. If DRO covers the full dynamic range of the sensor, it can't get better by bracketing. Right?
Auto HDR does it in camera, and you get what the camera gives you. If you bracket yourself, you can have much more control over the processed image. You can adjust shadows and highlights to suit what you think looks best.
I am not positivie, but I think the DRO setting gets more "agressive" with higher values. This could introduce more noise in exchange for more dynamic range. Bracketing would then let you choose how much noise you are willing to accept afterwards. I think.
Auto HDR mode also doesn't know what to do with movement in the scene. So you might get some ghosting. Manually, you can decide how to handle such a situation.
I also can't remember if all the RAW's are saved with Auto-DR, or do you have to be in JPG mode. If the latter, it kind of defeats the purpose since you are limiting yourself to 8-bit values. Manual HDR via photoshop can process the data into 32-bits per channel, which you probably have to reduce to 16-bit (or 8, ugh) for printing.
HDR captures three (or more) images and remaps the extended dynamic range into a single image. The term HDR is a bit misleading as it actually reduces dynamic range of a high contrast scene.
DRO works on a single image, remapping the shadow and highlight regions toward the midrange to bring out more detail in those areas.
I don’t use DRO, but I occasionally use in-camera HDR for still scenes where I can capture the image with and without HDR, and perhaps with various settings for it. I’m sometimes pleased with the result. Without HDR the highlights of this image were nearly blown out, and the shadows were nearly black.