Comparison between Stereo and 4 channels.
 

What does the option 4 channels in the emulator? In what it is different fom stereo or cloned stereo? Based on this, what of these options emulates better the Amiga hardware?

for me there is a big difference if you have a 5.1 speaker or a 4 channels speaker, the sound is really better, now if you have just a stereo speaker forget about this option or buy a 5.1 system speaker.

Both options require at least 4 speakers (2 front + 2 back)

4 channels: map each Paula channel to one speaker. Useless unless you want to wav record each channel separately. (instead of normal 2+2)

cloned stereo: clone front channels to back channels.

Neither emulates it "better", it depends what you prefer and how you would connect your real Amiga audio output (crappy multimedia speakers? stereo amplifier? home theater amplifier? I don't think you had those in early 1990s :D)

Ah, I thought these options emulated better the 4 channel output of Paula, but it is not exactly about emulation of the chipset. :)