I think you'll find that a lot of us here have switched from boots to trail runners. My own experience is that I have far more support for my feet, a much better fit, and a lot less weight with the trail runners.

Have you hiked around the house (preferably lots of stairs if you have them) for extended periods (i.e. several hours) with a full backpack?

I would suspect that the heavier boots will wear longer, but that's just a guess. Which is more important for you, longevity or comfort? Remember that a pound on your feet is the equivalent of 5 pounds on your back (per the US Army).