The "Big Apple", "Gotham City", "The City That Never Sleeps" or "Sin City", "The Marriage Capital of the World"? Which is better? Both cities are unique in their own way. The scenery is wonderful, the sites are amazing, the aerial view is just fantastic. You can definitely find something to do in both cities. Both cities can be romantic in its own way. Best of all, both cities are very historic.
To each is own I guess. In other words, it depends on who you ask. As for me... NYC all the way. Vegas is fun and all but it's one of those been there done that and unless I'm a chronic gambler what else can I do in Vegas. Once, maybe twice a year may seem like a lot but it's cool when you go with friends, get your drink on, play a couple of the tables, site see, etc. You also have to deal with people that don't know how to drink, the smell of smoke, etc. All tolerable things to have to deal with but why do I want to spend money on that stuff.
There's a reason why millions of people say I love New York. There's a reason why millions of people who have never been to New York City want to visit New York City. Sorry Las Vegas, I love New York! It's my "empire state of mind".