Any thoughts -- especially from those who live or have lived in Europe?
Don't know about the exact ratio of course, but the general relation will definitely be very much in favour of Model 3.
Reasons?
For one, size, as you said. Model S (and X) are really too large for many parts of Europe. Only yesterday I walked past the Model S that I usually see every day on the P&R lot of our local train station. And guess what, since I saw it last time it has now "acquired" some "nice" yellow markings plus scratches on the passenger side of the front bumper next to the headlights and wheelarches. A clear sign of having kissed a parking garage bollard similar to one of these:
Second, or rather for many first, price. The Model 3 is priced in the range of what many people can afford or at least what fits into what they have allocated as a budget for their next car purchase. The market for cars priced like a well optioned Passat, A4, 3-series, C-class is huge in comparison to the luxury segment in which the Model S and X are positioned.
Just for comparison, sales in 2016 in Germany (Jan-Jul):
A4 / 3-series / C-class / Passat
combined : 154,435
A7,A8 / 6-series, 7-series / CLS, S-class / Panamera
combined: 15,367
A ratio of ten to one, even just taking into account those 4 model series in the Model 3 price range. And that is not even taking into account all the other popular models in that price range, just the 4 bestsellers. Whereas in the luxury-segment, there isn't much more really than the abovementioned 7 model series. Ok, perhaps some Maserati, Jaguar etc., but sales of those are more or less negligable.