Why do Tube Amps sound more romantic v SS amps

I think it depends on your definition of "romantic" and other factors, such as personality types, venue, and where the specific "romantic" element is positioned on the classic sine wave of the evening's total love-making cycle.

I'll give tubes a definite advantage during dinner and foreplay.  After that, there are simply too many varibles to reach a solid conclusion, IMHO.  I'd use the common "thumbs up" term here for vaccum tubes but there are, most likely, other things that are "up" during this segment besides just thumbs.

The age and energy levels of participants could swing the pendulum one way or the other.  Also, whether one is an analytical chess player, or a "score right now" hockey player could be factors..  As for intensity, I can't explain why but the terms "slew rate" and "dampening factor" pop into my head, giving solid state the advantage.  And, yes, the venue.  An AirBNB is quite different than tent camping (both of which have zero chance of having a vacuum tube amplifier near by), so a solid state (most likely a Bluetooth speaker) will be the winner by default.  

In summary, I tend to be neutral on the tubes vs SS debate, and I'm sure either can rise to the occassion when called upon.

Everyone always brings up the distortion profile of tube equipment, which is generally true but triodes are also more linear that solid state devices, with simple designs fewer parts count.

Let us not forget that ALL recordings are PROCESSED and have some relationship to the actual "live" performance, but not all of it.

In the "old days," this processing took place on TUBE recording gear since that was all that was available.  When more sophisticated recording equipment became available, many times it was solid-state based.

SO, any recording you are listening to has the "imprint," if you will, of the recording engineer, the producer, the band members or orchestra director, and possibly others (marketing) in its final form. 

A simple example would be that in the 1960's, "pop" recordings were "mixed down" so that they "sounded good" on car radio speakers, which, in those days, were not exactly designed to reproduce accurate performances, but instead were going for a "sound" that would "sell."  (Buddy Holly is credited for "producing" his own music because he did not believe that a record company producer could create the "sound" that he had in his head.)

This is not necessarily "good" or "bad" but it is anything but "accurate."  About the best you can do for that is to get some master tapes, which, if modern, have been "mixed down" from 64-tracks (possibly) to 4 tracks to play on a home reel-to-reel deck.  You might also want to play some direct-to-disc vinyl recordings like those made by Lincoln Mayorga et. al. in the 1970's.  There are probably others out there as well, but this is a difficult and expensive process, so you don't get many and yes, even those are "processed" to some degree.

So, buy what SOUNDS GOOD to you IN YOUR ROOM and don't worry so much about the electronics.  For ME, personally, ARC tube HW playing through properly set-up Magneplaner speakers is the closest to "accurate" when reproducing processed music.  Everyone has their own idea of this, thus the myriad number of companies producing home audio gear.

Cheers!

If you want a romantic glow in your room, get an LED mood lamp to augment your SS. Won't burn your hands and is easy on your electricity bill.  https://smile.amazon.com/gp/product/B099WTN2TR/ref=ppx_yo_dt_b_search_asin_title

Listening thru a tube amplifier is still partially solid state. What do you think your streamer, DAC and other components are made from? Even within the tube amplifier the signal passes thru capacitors and resistors.

The difference is a tube amplifier is usually a transformer coupled design. No solid state amp I have ever heard be it for hifi or guitar amps truly emulates a transformer coupled tube sound. In the guitar world millions of dollars have been spent trying to do it with solid state and digital emulation. But never truly accomplishing that.

The main difference I hear with solid state is compression of the signal. A flattening of the sound stage.

I suppose there can be a more technical explanation of how electrons jump from the hot element inside a tube versus how they move within a solid state transistor that impacts the tone of the signal but I would not be able to speak to that with any certainty.