Here is a comparison that I posted on another board several months ago, just after the first non-Portland HD station was put on the air... KZEL Eugene, about 110 Miles distant.
I compared several HD units on my antenna (APS-9) tuned to KZEL from my location in Hillsboro. For different situations results may vary, but here is what I saw:
#1. Sangean HDT-1 tuner. Most sensitive, but #1 and #2 are quite close for my reception of HD from KZEL. I have seen RDS info from Seattle Stations (KING & KPLU) on this and the #2 Unit, but so far NO HD from Seattle.
#2. BA Receptor... this is a surprise, as many reviews say that the receptor is not very sensitive, but connected to an outside antenna it does well. Very close second for FM, AM not as good as HDT-1.
#3. Radio Shack Accurian. Fairly close, may have some HD dropouts while the above units are solid. When the signal drops to the point that the HDT-1 and BA are dropping out, the HD on the Accurian is gone. Better AM reception than the BA, no RDS.
#4. Sanyo HD1990M car radio (1st gen, no HD-2 reception). Fairly distant #4, will lock onto KZEL only on the best days.
I have also experimented with a Magnum dynalab 205 "FM Signal Sleuth" RF amplifier, and it does improve HD lock on all of the above units.
The HDT-1 has a readout of "carrier to noise ratio" (when locked onto a HD signal). Right now on KZEL I see 67dB with the amp on and 62dB with it off. Note...70dB is the best that I have seen on local stations.