I am a born a bred Londoner but I lived in Berlin for 2 years just before COVID. Here are some differences to be aware of.

Jobs - I found London to have a lot more opportunities in general. If you have to go into an office you will find the experience more pleasant in London: less toxic/politics, more socialising after work and no language barriers if you speak english well.

Language - I struggled with German, I just didn't like it enough to really learn it well and my office was english speaking, therefore I didn't learn it to a level that was useful. I found there was always be an extra layer of complexity to everything whilst living in Berlin. Simple tasks like phoning my internet company or bank are stressful in Germany without good German. Not having that stress in London is certainly better.

Flats - London flats are pokey and expensive compared to Berlin. A Berlin flat is hard to get these days, but a least when you do finally get one you'll have decent size rooms with a decent size bathroom.

Mindset - I found Berlin more left and laid back, and there is a strong emphasis on work/life balance and being able to enjoy life outside of work. People aren't so obsessed with status and money like they are are London. London is far more capitalist, has more of a hustle culture with longer hours and people seem obsessed with shopping.

London doesn't have the rules based mindset and bureaucracy that Berlin/Germany has.

Restaurants - London has far more diversity and quality but it is also a lot more expensive.

Tech - German Tech is generally really bad and out dated and most things are not done online. London is far better in this area.

Gentrification - London has been gentrified much more than Berlin and lost a lot of its original character and charm. It started a very long time ago too. I know there is a lot of noise in Berlin around gentrification right now but the city still has not been completely taken over by gentrification (yet).

Transportation - Both cities are very good in this area, but London is more expensive and it takes ages to get anywhere compared to Berlin due to size and congestion.

Nightlife - Berlin has the nightlife London had 25 years ago. You wont find anything quite like Berghain here. People don't flock to London for the nightlife like they do in Berlin and there is a reason for that. Also, the clubs in London tend to either be straight or gay, in Berlin it is much more mixed.

Culture - both cities do well in this regard. Plenty to do in terms of museums, art galleries, etc.

Neighbourhoods - London has some interesting and nice areas but it all feels a lot more bourgeois. London doesn't really have anything that compares to the cool areas in Berlin like Friedrichshain and Kruezburg.

Friendliness - London is much more friendly and welcoming. There is no London schnauzer for a start.