I can only do one city which would be best? Geneva or Zurich?
French vs. German. I like Geneva more. Nice old town, pretty areas by the bridge downtown. Take photos of the Jet d'Eau, and the flower clock.
Foodwise, I like Geschnitzelties (Zurich), more than Filet de Perche (Geneva), though.
I prefer Geneva. But neither one is high on my list considering what the rest of the country has to offer.
I preferred Zurich, although both were good for an overnight stay.
I wouldn't stay in either again though when there are so many lovely places close by.
I agree with the general sentiment, as my answer was going to be "neither".
Since you haven't detailed your itinerary or interests, it's hard to make a good
suggestion, but there are lots of options.