I have some preliminary empirical results and they match what I expected - the 2.4MHz demodulator is much better than the 2MHz demodulator.
This is from synthesizing ADS-B messages on a LimeSDR mini at various signal strengths and looping the signal back to a Prostick running whichever version of dump1090, then measuring the proportion of messages at each gain decoded by the receiver. (different message contents are used for each signal level, so the infrastructure can match up received messages with transmitted signal levels)
v1.14 never gets above about 70%, while dump1090-fa v3.8.0 reaches 100% over about a 25dB range. The overall dynamic range is similar if you’re generous with what you consider an acceptable reception rate.
Both versions were run with --fix --gain 49
and ran on the same receiver hardware.