I started using trekking poles to save my knees, which aren't in the best condition. Since going downhill is worse on your knees than going uphill, I've been using cane style poles, which I've found work better for this.
Recently I watched some videos of vertical kilometer races and saw that in some of the races, almost everyone was using trekking or Nordic poles. I wondered if they were really a help on steep uphills, so I ordered some more traditional poles to experiment with.
I weighed myself without trekking poles, then weighed myself with trekking poles taking the weight of my arms, but not pushing down. This took about 4 pounds off the scale. Then I pushed down with the amount of force I might use hiking. This took off 20 pounds.
My first real world test, I did a short stretch (less than 15 minutes) of steep trail with and without trekking poles. Yes, I've only done it once so far, and need to do it several more times. But the poles did save me about 25 seconds, but my heart rate was slightly higher.
One would think that the more I used these trekking poles, the more likely they would prove to be an advantage, as the muscles you use get in better condition.
On sections of trail that require some scrambling, I find poles to be an annoyance. They just get in the way. Packing them away and getting them out again seems like an inconvenience, so I haven't ever done that.
Testing is ongoing.