No it shouldn’t lose any quality.  Audiophiles will tell you otherwise, but audiophiles think 30 cent per foot copper cable is worth thousands of dollars because . . . stuff. 

As to the difference between analog and digital, it all depends on the DAC.  Once again, audiophiles will tell you a very expensive DAC is needed, but since even the most expensive DAC chipscost under $10 in bulk, that is a dubious claim also.  Sonos’ DAC is supposed to be improved from the one in the Connect, but not even Sonos is immune from specious marketing claims.  

There is a substantial difference in audio quality. If using your own DAC ( digital audio converter ) then you would be wise to try the digital output connection. There are people who don’t have sensitive enough audio equipment to be able to tell any difference and there are people who lack certain listening skills who may not be able to discern any difference. You really need to experience things for yourself. I can’t tell you if you like a particular wine and there are those who are unable to qualify wines. It’s a very personal thing. If you have a quality DAC, use it. It’ll probably be more revealing. That is not to say it’s always the case. Maybe you’ll prefer the RCA analog sound and rely on the digital conversion within the port.

Each to his/her own. Wine is perhaps an unwise analogy given the infamous test in which tasters evidently couldn’t tell white wine dyed red from the real thing...

Bear in mind, however, that the Port has come in for a bit of criticism for having a somewhat aggressive limiter on the digital out in Variable Volume mode, to guard against clipping. Fixed Volume into a DAC would be unaffected -- and would presumably be the favoured choice for purists anyhow.

The analog output in Variable mode also escapes this additional processing. FWIW the internal DAC chip is a generally well-regarded one.

Assuming you’re correct that one is unable to discriminate between red wine or colored white wine I imagine most of your listening is via a 1970’s transistor radio. The analogy is a good one, each based on a finer variations of a sense. I guess another simpler analogy that would be befitting would be that of a colorblind person matching an outfit. It may look fine to them and they’ll swear it’s fine but many of us perceive differently and think we know better.

Don’t take the bait folks.  The poster didn’t just join the board and dredge up a 10 month old thread because they want a rational discussion.  Two posts in and I count at least four insults to gear and ears, the audiophile’s only retort.  If they had any real trolling talent, they would have tried some sugar before the salt.  

Infamous only among the oenophiles...the rest of the world had a good laugh. Some testers even waxed lyrical about how a white dyed red would go oh so well with the food that suits a red.

So this is actually quite a good analogy to prove the opposite point. And if their shenanigans help subsidise the sensibly priced wines, all to the good. Unfortunately there are not that many audiophiles to benefit those that listen to music as music and not as a test signal.