Treking pole design is difficult, even though they sound like a simplistic piece of gear… not as complicated as a stove, for instance.
1) They have to support at least 75% of your weight. A larger diameter means extra strength for the same weight. But, the trade off is brittle and subject to side stress.
2) Joints are always a problem with strength. Every joint means it is weaker at the same weight.
3) Wear and tear can add up over a thousand hiking miles or so. Extra abrasion resistance and strength needs to be added to the tip area (about 14″ up) to prevent wedging in rocks, mud, and other trail obstacles.
4) Weight is very important. The lighter the better for the same strength.
5) Straps are necessary to support your arm/shoulder/body weight. Having a death grip on staffs to do this can mean expending a lot of extra energy.
6) A top handle for supporting your weight while descending should be about 1.5″ dia, min.
7) Generally accepted wisdom is staff length should be comfortable (with your hand setting up through the strap and handling the pole) at level with your fore arm. I tend to disagree with this (more below.)
8) Tips need to grip on a large variety of terrain: rock, gravel, sand, mud, etc. A softer steel tip works on all of these almost as well as a carbide tip, but has the added advantage of being extended about 3/4″ into mud, clay and other softer materials solidly. A longer carbide tip breaks at that length.
9) A small basket near the tip (about 1-5-2.0″ dia) helps in softer snow(actually larger,) mud, stream crossings, sand, but can get in the way of planting the pole. Some swift streams can drag pole tips up and back with any basket. About even, I would guess…
10) Reliable, reliable and reliable. As Erica says, safety while hiking, a prosthetic if the worst does happen and you are injured, and other ultra reliable uses that crop up on the trail.
11) Dual use covers a lot of different things. Measuring stick, tent pole, etc. A weinee roasting stick? Well…whatever works…
As far as staff length, I have found that in every case, I ALWAYS want a longer staff. Descents are obvious, with the staff well below me. Ascents means I want to be able to push forward and up, and, to catch myself if I fall backwards. I want a longer length staff for that. On level terrain, I want the staff to push me forward. Again it is behind me and longer than accepted wisdom.
The difference in weight between Ti, Al, and carbon is not real great, maybe a couple ounces. To me, a strict Ultralighter, the trade off is in weight vs. durability/reliability. I stripped everything off my staffs: joints, handles and heavy reinforcements for tips. Simple staffs have little to go wrong. But, they can be difficult to handle on an airplane.
I found that flick-locks occasionally failed catastrophically: broken hinges, catching on a rock, etc. There ain’t a fix for those other than a lot of duct tape. And they tend to catch scrub more than twist locks. Twist locks are heavier and more problematic, but are smoother to use and don’t fail beyond use.