This has been a meme forever, and while Leipzig has its own decent scene for its size, it is not remotely close to rivaling Berlin. Pick a decent sample of either established or up and coming DJs and compare how often they play in Berlin vs there to disuade yourself of that notion.
>and even Sofia.
Yeah, no. Just because a city has some parties here and there, it doesn't mean it should even be in the conversation in this context.
Well there's the problem. What you should compare is how many unknown new guys just making good music for fun in small unknown clubs visited by locals are there.
In my city I can go to a random non-descript bar with zero marketing or entrance fee, sit down peacefully with a drink, and hear world class techno together with few dozen strangers. Every evening. Doesn't feel that way in Berlin anymore, even if I pay it's all that global commercial style that the established DJs with promoter/management teams seem to fall into and the places are totally overcrowded.