How big is your property? If you have a lawn or garden that extends less than 100 yards from the most convenient power source, you may be able to use a corded hedge trimmer. However, if your outdoor space is larger or involves some odd obstacles, you'd be better off with a battery-powered or gas trimmer.
Do you want to cut branches thicker than half an inch? Most hedge trimmers are recommended to cut up to at least 1/2-inch branches. More powerful trimmers can do more, up to an inch or so of soft growth. However, if you need to cut something half-inch diameter or wider woody growth, you might be better off with a chainsaw or a manual pruning saw.
How often do you plan to use your hedge trimmer? If your plants only require occasional trimming (a few times per year), then a cheaper electric or cordless model makes sense. For more frequent jobs, spending the extra money for a more powerful gas trimmer can save you both time and money in the long run. Keep in mind that regardless of the power source, residential hedge trimmers are rated for occasional use only
Do you need hearing and eye protection? For professionals using any power tool (including hedge trimmers), the industry standard is to use both eye and hearing protection. Homeowners would do well to follow suit; although many hedge trimmer manufacturers don't release the decibel ratings for their tools, some models definitely exceed the threshold for causing damage to your hearing. Wearing earplugs is a cheap, comfortable way to protect your hearing; we provide a full report to help you choose the most comfortable and effective models.
Gas or electric? Gas hedge trimmers have been the gold standard for professional landscapers for a long time, but top-rated cordless models have closed the gap. Skip models powered by older NiCd technology and go right for cordless models that use Li-ion batteries. They are lighter in weight and provide consistent power output right until the battery peters out. Corded electric models are terrific for lightweight trimming tasks on smaller suburban properties, and are among the least expensive type of hedge trimmer you can buy, but they don't have the cutting ability of gas models or the more powerful cordless ones.