Tecsun - PL310 vs PL380 dB meters

I use Tecsun radios for portable station finding and listening. Ujima 98FM is a community station in central Bristol, and just North of Bristol it comes in the weaker of the two community stations currently on air. I used it for this test as it is a good example of a weak but audible station. First, the PL-310 without being affected by inductance from my hands / body was reading around 4dB on the level and 0 on the S/N meter. Second, the PL-380 without being affected by inductance from my hands / body was reading around 18dB on the level and 0 on the S/N meter. With inductance (holding the radio, or trying to record holding the camera close) I can increase these to 6dB level and 1 on the S/N for the 310, and 20 or 21dB and 1 S/N for the 380. There are major differences in the readings for some reason, yet the reception (though you can&hear it in the video so much as on the 380 I had to hold the camera away and zoom in) sounded roughly the same. When I get my 2nd 310 in a few weeks, we&see if there is a difference even on the same model. BP