Here's how I look at HREW vs DOM...
HREW, I'd use in a truck that was a street driver/wheeler/trail truck/dd. Something that, if it was rolled, would essentially be totalled (from a street driver perspective) and need to be replaced. Either replace the body only along with a new cage or build another truck completely. I would use HREW in my truck because cost vs the one time it will be used is my deciding factor.
DOM, I'd use for two reasons. 1st being a rig that would be more prone to being rolled repetitively. This would be a purpose built rock rig, trailer queen, rock buggy, competition buggy etc. Something you would roll, flip it back over and keep going many times throughout it's life. 2nd would be the Suzuki or Jeep that needs a cage but can't be tied down with 500lbs of tubing and weight savings is real critical.