When I first came to work in London I was quite happy. The place was international; so many things were happening there. Best of all, I could continue to speak English and live on my own, whereas my default situation in the Netherlands meant staying at my parent's house and enduring all the traumas that came with that. So I was, in retrospect unfairly, biased towards London.
I've worked in London for two years now and I think I have a reasonably clear image of what kind of city, and what kind of country, it is. The UK is a second-world country pretending to be a first-world country. The only reason this somehow works out is that London has jobs, or at least more so than most anywhere else in Europe. If I were to start my life from scratch from a neutral origin, not knowing anyone in either country, there is no doubt in my mind that I would prefer the Netherlands over the UK. The Netherlands is better than the UK in all of these things: proper health care, proper houses, proper roads, proper cycling paths, better quality food, more accessible nature. The UK wins on: having hills, more variety in landscape, a more interesting capital. In terms of safety I'd rate Amsterdam safer than London, but not by much, and it's never really an issue in the countryside.
But of course things are never that simple. Nobody starts completely from scratch. I am Dutch by birth and so the choice between the UK and the Netherlands is between staying in my home country and a foreign country. Each has its advantages but my stance is far from neutral.
I cannot deny that I like the way British people completely ignore each other. There is zero sense of community or even interaction with the people living right next to you, something which is very foreign to me. But that's the way I lived in Japan, and I quite like being left alone. At the same time this sense of mutual ignoration brings with it a sense of danger and uncaringness that I dislike. If you don't know your neighbors then you're more likely to suspect them of stealing your shit than you are of hoping they might help you if you're in need.
So, Netherlands or the UK? My cynical answer would be: go wherever you get paid the most, which is most likely London. But that's an answer for a 50-year-old, so for now I'll say: come back to either country when you're old, go anywhere else while you're young.