We have used Leki and Black Diamond, both good. We do a lot of bramble and nettle bashing.
The folding poles are very convenient, especially on buses and trains, but we have found them fragile and several have broken.
DO NOT use folding poles for vegetation bashing! They break!

I've been using a pair of Black Diamond Trail Pro Shock Walking Poles for over two years now and have found them very reliable. I like the ease of adjustment and not had any problems with the clip mechanism slipping. I tend to use only one for local walks around The Malvern Hills but find the two very useful for steeper ascents and descents, for example, in The Lake District.

The newer types of foldable poles are a great idea, as they can be more easily stashed to your rucksack (daypack or other) when not in use than the telescopic varieties, which tend to be longer even when furled and either stick up (catch on branches) or stick out (catch in kissing gates or squeeze stiles, danger to other people when you turn). There is a problem with them, however, namely that the unfolded lengths may have sharp edges - I've minor-cut myself more than once when opening the rucksack. My previous pair were Trekmates, very light but not long-lasting, especially when used to bash nettles. Current ones are Robens, whose release catch is at the bottom rather than the top, so more likely to be damaged or gunged up (and needs regular oiling); since I haven't used public transport for a walk since March I haven't had to stash it folded, something I will be doing soon.

Even with lightweight poles I've managed to get three years use out of them before they either break or refuse to fold. Experience of heavier telescoping ones was that the fasteners became worn (the poles tended to 'shrink' down in use) before the tip or ferrules, hence my preference for foldable ones. Even the heavier ones didn't survive being trodden on (they refused to telescope), something that may be less problematical with folding ones since they could survive with a single bent length. Another advantage of lighter poles is that they're less expensive (the Robens were v.cheap). NB A major danger with folding poles is that in an emergency (eg. keeping upright in very wet ground, or as a support on steep snow) they may come apart just at the wrong moment, exposing you to their sharp edges (and loss of support). The advantage of the Robens poles is that the (wrongly placed) button catch holds the lengths together while in use.

I have been using walking poles for many years now. My original Leki poles with antishock suspension and cork handles are still going but bottom sections rather warn.. I lucky enough to pick up a similar pair with black rubber/plastic handles in a charity shop a few years back but the grips have now gone soft and sticky so now time to replace them. Tech seems to have moved on a pace.
I tend to use the poles to bash overhanging nettles and brambles at times so would like thoughts if it is best to stick with Aluminium poles or try the foldable Carbon fibre poles as I have a feeling these will be more susceptible to damage. I am just over 6ft tall and 12 1/4 stone. Slightly reluctant to venue away from Leki but it seems Black Diamond also crops up quite a bit. Also may stick with antishock, but some of the upper range of poles don't have this anymore.