That's a tough call, Nadine; the Gardens are beautiful but so is the city. It's been years since I was there and things change, but it seems like it was about half an hour to the Gardens and I don't think we saw much of the city. It should still be dusk that far north, and with the lighted fountains and landscape, absolutely beautiful. I only saw it during the day but I can imagine how beartiful it must be at night.
And the city must be beautiful at night also; but my guess is you just drive through it en route to the winery, which I have had my fill of also.
If it was my choice I think I would go to the Gardens; but hopefully some of our members will have more up-to-date information for you.