I've lived in both cities. Really depends what you want. New York is a city that you immediately fall for. London is an affection that grows steadily on you over time.New York is more fast-paced and far more dense. It's more obvious exactly what is open late until 4 a.m. and what isn't. The city has an energy that stretches the limits of how long you think it is possible for a human being to be awake. Public transportation is very, very cheap and it's fast to get from one side of the city to the other. On average, if you were to pick a random restaurant, I think the food is better. London is more like a collection of villages that have grown into each other over 1,000 years. It's lower density and I believe it takes longer to get from one side of the city to another. The Tube only runs until 12:30 or 1 a.m. (But the really edgy part of London -- Hackney & Dalston -- is only a short bus ride or maybe even walking distance from the financial center if you're liberal about what you consider its boundaries. Lower Manhattan, while extraordinarily fun to live in, is over-commercialized. The unique little shops and curiosities that made it an unusual place to live increasingly feel more like a vestige of the past to me there. Chains are kinda taking over.) I personally think the artistic culture is far less commercial and much more innovative in London than New York. The Arts Council supports all kinds of local, eccentric and home-grown projects. Fashion is quirkier and more original. Alexander McQueen, I think, could have really only come from the U.K. and Central St. Martins. New York's designers and artists think about what will sell. London's artists think about what is conceptually new, even if it is difficult and considered unattractive now.London is also a more international city than New York. (I say this somewhat controversially). While about one-third of Londoners and New Yorkers are foreign born, America encourages more of a hyphenated sense of identity. People are Mexican-American, or Ethopian-American, or Chinese-American. In that sense, while New York may be international, the U.S.'s comparatively prohibitive immigration policies mean people try to stay in the country for a longer period of time and become more assimilated than they do in London, where dozens of other countries are literally an hour's flight away. Travel, of course, is a major plus in London. You can you get away for ~$100 to Andalusia, Morocco, Turkey, Berlin, Milan, Rome, etc. Travel is deeply ingrained into the culture and Londoners now legally have five weeks of holiday a year.London's food culture is improving, but you really have to know where to go and when. Over the past several years, Brits have come to embrace and elevate their own cuisine and local produce. I love the different mix of international cuisines there too. Growing up in California meant I considered Italian, Mexican and Chinese to be the great trinity of foreign cuisine. In Britain, chicken tikka masala and the Turkish kebab rule. Sunday roasts also seem to be the functional equivalent of the Manhattan brunch. One of my favorite things to do in London was get lost in the Sunday markets -- Broadway Market, Upmarket, Borough Market, Brixton -- really, any of them. There are hundreds of stands where you can find the best hog roast, cheese brought in overnight from France, nduja from Calabria, octopus balls, banh mi, spanakopita, curry, Ghanaian stew, bizarre T-shirts or whatever. If you want to stay out very, very late, you also have to know where to go. Most places close down around 1 or so. The drinking culture is also far more onerous on your liver. A week of Manhattan drinking is more distributed. It might involve cocktails and wine on several nights, with some extra drinking on weekends. A week of London drinking and the culture of buying rounds -- where everyone is expected to buy a round of drinks for everyone else -- means you end up drinking WAY more than you should. If I went out drinking with a group of eight people, all eight people would end up buying drinks for everyone else. And then I would buy eight drinks for everyone (which is way more than I would ever pay for in the U.S. being a small-ish woman).If you're American, it's much easier to find a social circle in New York. Americans are just much more open to loose and sudden friendships. With Brits, you have to know them for at least a couple months until they feel really comfortable with you. You can apply this same line of thinking to dating -- except when Londoners go on the lash, which is probably the only time some Brits feel truly comfortable with themselves. (Just teasing!) In New York, the upside and the downside of dating is the paradox of choice. Enough said there. There are entire TV shows, movies and books devoted to this problem. Almost every New Yorker will tell you that they love the city and would have a hard time living anywhere else in the world. Virtually no Londoner will tell you the same thing about London. They will moan about the weather and reminisce about their holiday in Phuket, Ibiza, etc. Don't mistake this for misery (most of the time). Brits and Americans just have different ways of expressing themselves. Londoners find our flagrant use of "Amazing!" "Awesome!" and "Love!" as tiring and insincere as we find their lack of eye contact and smiling (amongst strangers) cold and dispassionate. Also, talking about what your job is or asking the requisite "What do you do in the city?" question immediately is a faux pas in London. The vulgarity of that question also probably has a little to do with how Britain is a class-based society where a person's stature in life should be readily apparent through their accent, demeanor and dress to other Brits. This isn't the case in the U.S. so Americans tend to probe more, especially in New York, where a person's career is a major -- if not the most important -- part of their identity. Then of course, there's the cliche that Americans live to work, while continental Europeans work to live. The British tend to be somewhere in between those extremes. In Britain, frivolous banter is a high art. Talking about nothing can be a way to probe a person's intelligence, wit and creativity.I can't really compare costs at this point since the pound is so weak. When I lived in London, GBP-USD ranged from ~$1.40 to $2.10. When the pound was hovering near its peak, the daily costs of living were extraordinarily high, but rent took up a comparatively smaller share of my monthly income than it did in New York. Health care is also free (er, nationalized) in the U.K. I can't speak for older people who are likely to have more serious health problems, but for a younger person in good health, this was awesome. No having to stress about what's covered and what's not, figure out who is a provider and who is not, be shocked by unanticipated co-pays that were not listed in the original health plan marketing material, be sent random $200 or 300 bills for a routine annual when your doctor for whatever reason can't bill your health insurance provider, have expensive, unnecessary tests or consultations pushed upon you, worry when you're in between jobs, or re-figure everything out again when you change jobs or your company gets acquired. Also, the very best essay I have ever read about the experience of a young person in New York was written by Joan Didion: http://www.mtholyoke.edu/~zkurmu...