The Best Decision is an Educated Decision.
Selecting your knitting machine should be done carefully. Just as there are different knitting sizes and crochet hook sizes for different sizes of yarns, there are various gauges of knitting machines. Take your time to learn what models knit the size yarns you want to use. Often the requests I get are "I want to do hats." Hats can be knit in any size yarn. There are hats knit out of thick yarn, and there are hats knit out of thin yarn. Thin yarns are better knit on the standard guage machines, while hats done out thick yarn need to be done on a bulky knitting machine. Understanding which machine knits which size of yarn, and understanding the features each machine offers you, is the key to making a wise choice.
Read these articles to help you decide which knitting machine is the best knitting machine for you.