Haven't worked in NYC but I've worked in London for 3.5 years and am in the process of leaving/going remote because I don't rate the quality of life here at all and I'm exhausted from it. Things that take its toll for me:

1. Too. Many. People. You can barely book a restaurant or get a seat anywhere. 2. Nothing works. Trains, airports and mobile network reception. 3. Commuting. Rush hour is crowded, the tubes are disgusting, getting anywhere across town takes at least an hour so you rarely want to risk trekking somewhere unless you know it will be worthwhile/you can get in. 4. Renting / moving house is super stressful. Estate agents are constantly exploiting you.

A whole bunch of my friends raved about London a few years ago which is why I came out but I don't think it is what it used to be. That being said, there is a lot of opportunity here and you can earn well if you hustle. I'd suggest you look at starting out as a contractor.

I think there are better places to live and work in tech, in other European cities like Berlin, Stockholm and Amsterdam.