Nothing really wrong with any of those approaches and the best fit varies with application. A few thoughts on each though;
- 'solid aluminum' active with massive cabinetry (ie, 400lbs) route
I don't like solid aluminum by itself, best when combined with other materials like birch plywood so the...
You hit that point right on, to actually make a difference in this aspect you need massive amounts of extra weight, the difference in weight of something like our 18.0, 115lbs vs your DD18 at 142lbs, makes no difference whatsoever. You have to get into the several hundred pound class to be worth...