I'd go with the London offer solely based on "man, I'd really love to work with that person". In the early stages of your career, it's best to optimize for peop

I'd go with the London offer solely based on "man, I'd really love to work with that person". In the early stages of your career, it's best to optimize for people. The best investment you can make is work with people you admire and want to learn from. In the long run, relationships matter more than anything else. All other things - stack, languages, cost of living - are temporal. Quality of people and relationships are valuable long term. Good luck!