Weed Trimmer Buyers Guide
The basic concept of a trimmer could not be any more simple : spin a plastic string really fast and cut down grass.. Making sense out of all the features and buzz words is not nearly as easy.  When choosing a trimmer there are several important factors. Conditions come first. If your goal is to just clean up a few stray clippings along a fence an inexpensive consumer model will do just fine. If your out to clear brush for a new home you'll want a powerful unit capable of tackling woody material. Versatility has become a popular selling point as well. Many models offer the ability to tackle a variety of tasks like edging and trimming hedges. If this is a real consideration pay close attention to the build quality of the driveline as these chores can cause high shock loads on the drive components. Weight may seem unimportant, but your back and arms will surly know after a half hour in the yard.

 
  • Drive Line - Options are typical cable, solid shaft or hollow shaft. If the manufacturer does not state the driveline always assume its a cable. Solid driveshafts last longer and are suitable for high shock loads caused by metal cutting blades and attachments. Hollow shaft options are geared for commercial landscapers because they offer durability but are ligher weight. Cable drive is the most common and found in nearly all consumer models. Its an acceptable drive and the only option for curved shaft models.
     
  • Engine displacement is a measurement of the size of the engines cylinders. Typically a trimmer with more displacement has more power. Today this logic is skewed some as many units will share a common engine, but by tweaking compression and fuel ratios the manufactured can change the true power output. The most reputable brands publish both engine displacement and horsepower so you know what your getting.
     
  • Line Size and Type.  Larger line will last longer, but at an expense of tear the grass rather than cutting it more smoothly. Some companies sell square line and promote it as a more effective cutting surface. While some people swear by a magic type of line, others point out that its snake oil science and marketing hype. Typical sizes are 0.065-0.130.
  • Anti-vibration. Anti-Vibration features are present on most models and help make a trimmer comfortable to use over a long period of time.
     
  • Head Type. There are dozens of different types of string heads. Most revolve around the concept of bumping a button on the ground and allowing inertia to pull out the line. A new popular option has been a head that takes pre-cut pieces of line that can easily be locked in place. This is a convenient way to service the head but there is a high amount of waste line and it requires frequent replacement. Plastic blades are the best long term alternative to those avoiding a serviceable string head. Lastly, high end trimmer can support metal blades that can be used for a variety of uses from grass to saw blades for cutting small trees.
     
  • Handle Type: Most companies offer a loop or bike handle style trimmer. Loop handles are compact and easy to use. Bike handles are more comfortable but require a shoulder strap to support the weight of the trimmer. Aggressive blades often require bike handles so that the operator can keep a good hold on the trimmer incase the blade strike something hard causing the unit to kick.
     
  • Engine Type: New emissions standards are driving companies to develop new engine technologies that burn clean but still produce good power. Many companies have not been able to get 2-Cycle designs to burn clean enough so they have turned to a 4-cycle system. 4-Cycle engines are typically heavier and not tolerant of being run upside down. Some companies like Stihl have build hybrid designs like the 4-Mix that offer the best of both worlds.
     
  • Weight: Clearly lighter is better. Trimmer typically weigh 10-14lbs and do get heavy with prolonged use. A lighter trimmer will cause much less fatigue after long use. 
     
  • Durability: Most repair shops estimate the life of an inexpensive consumer trimmer at 5-8 years under typical operating conditions. Commercial landscapers who put well built units though heavy use are generally happy to get 3 years out of the best trimmers, in the hands of a consumer 10-12 years is not uncommon. Spending more money for a better unit may buy you a model with more desirable features and cost you the same amount over several years.