Let us start with …

Yes, it is really that simple. There is nothing more to add to that.
Well okay, I will explain a bit …

Accessibility

Let some hard facts speak for themselves:

• Accessible tube stations in Berlin (BVG zone A): 47 out of 96 = 49%.
• Accessible tube stations in London (TFL zones 1+2): 17 out of 132 = 13%!

I do not know the perspective of a wheelchair user, but I once had to move a very heavy suitcase from Willesden Green to Plaistow and had to change twice. There were a lot of stairs, hardly any moving ones and no lifts at all (minus one point for the public transport system). But there was always someone to help me carrying the suitcase up and down the stairs (plus one point for the Londoners).

That could not have happened in Berlin. (Ambiguity intended.)

Cleanliness

Whenever I mention to Londoners that the London tube is so much cleaner than the Berlin tube, they are very surprised. Most Londoners find the tube in London very dirty indeed. But they obviously do not know the Berlin tube, especially not when it runs through Kreuzberg. Where else can you see garbage, vomit, condoms, broken bottles and blood stains all in one compartment?

I wonder why the tube in London is so clean.
Is it the extreme security? After all, every piece of garbage could potentially be a bomb.
Do they have more money to hire more cleaning staff? Possibly.
Or do Londoners just behave themselves? Highly unlikely.