Hi JJO,
I have a reconstructed knee and started using one pole back in 1995. I liked it so much I went to 2 poles in '96 and never looked back.
I have gone through about 4-5 complete sets over the years , mostly Komperdells and Advance Base Camp (ABC) which I believe became LifeLink a number of years ago. I believe that there are only 3-4 pole makers out there now - Leki, LifeLink and Komperdell and Black Diamond - I think this covers most of them.
Black Diamond (BD) uses an exterior flicklock, the rest use an expanding interior cuff, where you twist the poles to loosen the cuff and adjust the length, and retwist to tighten the cuff. I can't comment on BD's though I have heard nothing but good comments about the flicklock design.
The Leki and Kompers look very similiar, but you can tell them apart easily by the basket attachment (Pegs denote Komperdells - The basket twists and locks into place). Komperdell makes the EMS proprietary brand and a few others. I don't know who makes REI's. Leki's also tend to run a bit more expensive than Komperdells, but seem to last longer.
As for style, I like the 3 section plain poles with no anti-shock attachment. I wait until they are on closeout somewhere and pick them up as cheap as possible. The 3-section models usually close a little smaller than 2 sections and are easier to get in a duffle (IMMHO) when flying and seem a bit stronger.
I usually can get 3 years out of a set of Komperdells, The Leki's that I got in '99 are still going strong, though I have replaced the cork grips and tips already. I do beleive you get a better pole with Leki.
The insides of the twist lock poles (aluminum)will corrode into powder over time, making the mechanism tricky at best. Never use oil to lubricate. I find I take my shotgun cleaning brush and take the poles apart, slide it in and clean oxidation as much as possible and they work fine for another year.
I also have a set of old ski poles that I sometimes use, though I rather like the ability to collapse my poles and attach them to my pack so that they are not lying crooked or moving around scratching the interior plastic walls of my auto.
Check Sierra Trading Post, REI-Outlet or Killerdeals.com for closeouts. Check that the closeouts are not due to material or manufacturing flaws, but rather overstock or design change. A pole with a weak spot in the aluminum would not last long.
Hope this helps
Rick