So your amp sounds best to you when you dial in a little feedback big deal. It does not tell you that all amps should sound better that way. It is very hard to design an amp without feedback. My hutch tells me that if your amp were designed to sound its best without feedback and then give you the choice you would prefer no feedback. This goes back to the Manley amp that allowed you to listen to their mono blocks in single ended mode or push pull mode. I liked it better in push pull mode and then thought that single ended amps suck. Oh not true, you can't design a circuit to sound good doing both you need different transformers and parts. So you see my friend your conclusions on a simple rotary switch is not viable. You need to keep an open mind which at that time I did not and now do.
Negative feedback Amp=more faithful reproduction?
Negative feedback (NFB) vs zero negative feedback (ZNFB). There seems to be unsubstantiated contention that ZNFB amps sound more realistic. I know this is an age old debate favoring the ZNFB design, but I think most audiophiles have never bothered to look into this matter and believe the advertisements and proponents of zero NFB design. I have been in that camp until recently. My own experience and research into articles on this matter leads to me believe NFB is needed for faithful reproduction of music. I'm not saying NFB design is more "musical", which is a highly subjective term and usually means more euphonic or colored. I've posted a similar question awhile back, but I was hoping we can have a more evidence based discussion on this matter. Perhaps, we need clarification of descriptive terms we use to describe sound. My contention is, in general, NFB designs produces a more accurate or faithful reproduction of music than ZNFB designs. Here is a very good article on feedback and distortion:
http://sound.westhost.com/articles/distortion+fb.htm
http://sound.westhost.com/articles/distortion+fb.htm