ELI5: What is the difference between stable and weekly?

[KDMultipass]

How does the xiaomi.eu team pick what version is stable?

What are the advantages and disadvantages of flashing either rom?

Are they even compatible in terms of dirty flashing?

 

[cobben]

Xiaomi.eu does not "pick" them.
Xiaomi does.

I'm my experience dirty flashing to stable from developer does not work well.
From stable to developer often does work well, but no guarantees.

The stables are always derived from older versions of developer, sometimes much older.

Imho a good developer is often much better than a stable, but that is my preference.