I did a quick search, and couldn't find any threads where this particular question was addressed as a specific topic (there were a few where it came into the discussion incidentally.) I thought it might be useful to have a specific discussion to help new hikers.
Question: Strictly for hiking, do you prefer to hike without a pole, with a single staff, or with a pair of trekking poles?
I'd prefer not to clutter the thread by discussing the auxiliary use of the poles as shelter supports and the various shelters available; that's a thread in itself. I'll stipulate to the very valid point that, if you are committed to lightweight hiking, a great way to save some weight is to select a shelter that uses your trekking poles to support the shelter, eliminating the need for separate tent poles. In addition to plain old tarps, there are a number of specific shelters out there: the Lunar series from Six Moon Designs leaps to mind, along with several models of the excellent TarpTent; MSR has a couple like the Twing and Twin Sisters, and just added the Fast Stash, a reintroduction of a design that they discontinued a few years ago. Black Diamond also offers some of these, as does Integral Designs and Granite Gear. Most such shelters are single-wall, and highly functional. There are also some, like other TarpTent models, that combine a single tent pole with a pair of trekking poles to optimize the setup. There are also some pyramidal-shaped shelters that only require one pole; however, some of these allow the use of "linked" poles to get increased headroom. If you're a new hiker, and interested in this approach, check these shelters out, and start a new thread if you have questions.
Because these shelters are all covered exhaustively in other threads, I'd prefer not to rehash all that here, and limit this thread to the relative merits of hiking with or without poles, using single vs. double poles, and related topics such as flick-lock versus twist-lock, anti-shock versus no anti-shock, and collapsible versus fixed.