There are many options and even more opinions in the world of in-ear monitors.
And when it comes to in-ear monitors for musicians and live sound techs, it is extremely important to consider the key variables that define the ideal in-ear monitor.
Needs for musicians and vocalists will vary slightly from those using in-ear monitors for live sound mixing (like the monitor mix engineer).
Musicians and sound techs alike will benefit from a good fit and accurate sound reproduction, but an audio engineer will likely want extra noise isolation for more defined monitoring. And musicians may prefer more or less stage noise bleed through their monitors.
What musicians need from an in-ear monitor...