There are several factors to consider when buying a metronome. The first thing that many people look at is cost. If money is an issue in your decision making process, try MetronomeBot. The online metronomes are all free on this site. If you are looking for a simple metronome to use on your phone or iPod, try the MetronomeBot mp3 files.
If your budget is more flexible and you are looking for an individual metronome which you can keep in your instrument case or leave on your piano, there are several other factors to consider: the loudness of the metronome, whether or not it has an output jack for amplification, extra features like subdivided beats and speaking the beat, and ease of use.
Read the following reviews to find the best metronome for you.
Boss metronomes: Loads of features. Their models include small, lightweight metronomes, as well as the most advanced metronome available: Dr. Beat.
Korg metronomes: review coming soon
Yamaha metronomes: review coming soon
Wittner metronomes: review coming soon