The closest you'll get to Italy from Vegas! Haha
We opted for a shared gondola which we didn't mind because the private gondola is too expensive for a 15min ride. I don't think sharing a gondola with a couple you don't know makes the experience less romantic or less fun (unless the couple you're with is unpleasant) :P
You can either do the indoor or outdoor gondola ride. We were in Vegas during winter season so we stayed indoors even though I would have preferred the outdoor gondola ride. Enjoy!