Grx Medical Cd-27 vs. Cardiology III

I was wondering if there is anyone who has tried both of these steths. I am curious if they are REALLY comparable (like they say). Grx medical doesn't have an acoustic rating on their website like littman does, so I hope I can get some input! Thanks!
(Btw, I know the littman has tunable diaphragms and the grx med. doesn't, I am more curious about acoustic quality)