Dave Dugdale compares the Rode Lav with the Rode PinMic and Sennheiser ME2 for sound quality and connectivity options:
The Sennheiser ME-2 lav mic is a sibilant for speech around 3kHz to 10kHz, it almost sounds like the “S” sounds are a little distorted, so even if you use a De-Esser it stills sounds nasty in the high end. The Sennheiser on me doesn’t sound too bad, but watch out when you use it on a female that has a lot of sibilance. However both Rode lav models work well in this region. Now having a rise in the frequency response curve is not a bad thing for when you want to hide the mic under clothing, also you are not speaking directly into the mic so the higher frequencies will roll off.
Read his blog post here.