How can you know "what to listen for"
There’s a post a member put up a couple of weeks ago (go find it), who does mods for his customers, where he takes a Mosfet amp removes the complimentary N/P channel Mosfet output stage and replaces it with complimentary NPN/PNP Bi-Polar (BJT), and he and his customers say it all in their description of the sound change.
That’s why I said if you live with the two for a while you will hear the difference.
If you read what was said at the seminar, you can apply that to what you might hear, again especially on the harder to drive speakers.
I hear Mosfets into my hard to drive speakers as "polite" but a bit of a "yawn" that lack that punch, drive, boogie factor, and an openness that BJT’s have that can also be detrimental with bad recordings.
Some call it "Mosfet Mist" other call it "Tube’ish" I think maybe it’s because they aren’t as linear as BJT’s just like tubes with with 2HD as outlined in the seminar.
Cheers George