In this video, Dave Casler, of “Ask Dave” fame, uses an RSPduo together with SDRconnect to compare the Goozeezoo K-180WLA active loop antenna with his main station Chamelion loop antenna

And here he looks at the very popular MLA 30+ magnetic loop antenna:

The RSPduo is ideal, with its dual tuners and SDRconnect provides accurate signal strength and SNR readings. Together you can compare the same signal being received by two antennas at exactly the same time.  This overcomes the problem you have on HF and MF  frequencies where signals are bouncing up and down in strength all the time! Check ou the RSpduo spec here: https://www.sdrplay.com/wp-content/uploads/2018/05/RSPduoDatasheetV0.6.pdf