I have a 50D and a Promote Remote. Like you I bought the Promote to extend the camera control, especially as I am an HDR biased photographer.
I have a very simple view of the benefit of ML vs the Promote. If you have the Promote get ML, if you have ML think carefully about getting the Promote.
The Promote will give you greater and smoother control when doing timelapses, and of course Promote is not a video controller.
I have no hesitation in saying that ML scores on bracketing for subsequent HDR processing. Why? Because you need no additional cables or hardware than your camera. You can travel light.
Additionally, ML bracketing has what I think is a killer feature: auto HDR mode. That is ML decides how many brackets to ensure the full dynamic range is captured. I usually use the auto HDR mode these days. I do not need to do any metering to decide how many brackets I need.
Bottom line: get ML in your 5D, as you are an HDR bracketeer!