Lobby: To whom do I report- GPS does not match MMR values?

So- I've been using MMR since mid July, I believe, and have been very happy to have it, both as a training/logging tool and a way to keep me motivated. My GPS was also dead during this time and I could not use it to keep track of my mileage, so this site was especially helpful. Thanks!

 But, I recently replaced said GPS, and have found that the new unit (Garmin Etrex Legend) records shorter distances on my runs than the mapping function at MMR. I've gotta guess that the GPS is correct, and that the Google maps functionality which I have supposed MMR uses is somewhat, um, squishy,or inexact? So, my questions is: To what degree have other users noticed errors in their MMR logged runs vs. GPS readings? 

So far I've seen .5 difference in a 6 mile run (GPS reads 5.97 and MMR reads 6.45) and .25 or so in a 10 mile run (GPS reads 10.0 while MMR reads 10.24). Once I've found the correct cable for the GPS I'll download my run logs and compare them directly to my point and click MMR logs, and see if it's possible that the difference lies there.

 Thanks.

 Steve