I've seen walking poles range from <£10 to >£100 - and to a casual observer there doesn't often seem to be much to distinguish them, with both having good grips and shock relief / suspension. What makes one better than the other, and is it worth investing in one which is more expensive if it's going to be extensively used?
Each person is unique and may need one feature over another. But here is my take on the features in a rough order of importance:
Warranty: If you plan on heavy usage, make sure it has a lifetime warranty and a manufacturer that backs it up. Many will find a way to replace it in the field.
Weight: If you're backpacking, saving weight is important.
Comfortable handle: You're going to be holding these all day. Make sure they don't rub anywhere that would result in a blister. Make sure you can keep your grip when sweating, and make sure the wrist strap holds on without getting in the way.
Adjustable/compact: If you want it to easily pack in the trunk or in luggage for a flight, this feature is necessary. Some level of adjustment is useful to shift from climbing uphill to braking downhill. Check the quality of the adjustment locks, you don't want them to slip when you're bracing yourself from a dunk in the river, and you want to be able to easily fix any problem in the field (preferably without carrying a set of wrenches).
Steel point: You want this to hold if you press against a rock, and not slide all over the place.
Snow baskets: If you plan on using these in the winter, these will keep you from plunging all the way to the ground with every step. Otherwise, they're not really important.
Shock absorption: I passed on this feature, but I can see it being useful for those with joint problems.
A good set of poles should last a lifetime, so don't be afraid to spend a few extra bucks on a better model. If you're about to be attacked by an animal or you start sliding towards a cliff, you'll be glad you didn't trust your life to the cheapest thing you could find.