Using a Connect (if you can find one) or a Port you are forcing a “hop” of the audio stream from the TT to another Sonos speaker. Using the Amp with 3rd party wired speakers or Play 5 line-in the audio stream from the TT is direct. That’s not to say that the audio using a Connect or Port is not good; I just prefer a direct connection whenever possible.  FYI, the TT must be pre-amped either internally or externally. 

Do you mean the RCA’s are better than the 3.5mm input?  If so, then no, not at all.

Really? Huh idk why I thought 3.5mm wasn’t as good at separating stereo sound.

So seems like price/availability aside, Play Five is the obvious choice if I want to listen to a turntable and occasionally play it throughout my Sonos ecosystem.

Thanks for the quick answers!!

A lot of things you hear about audio is utter BS, meant to puff up audiophiles and drive sales.  For a line-level signal, a 3.5mm connection is indistinguishable from RCA.