Kachchi vs pakki — the core technique split
The single biggest difference is whether the meat is cooked before going into the pot. Hyderabadi (kachchi) layers raw marinated meat with par-cooked rice and finishes both together under a sealed dum, so the meat juices cook into the rice from the bottom up. Lucknowi (pakki) cooks the meat in a gravy first, then layers it under par-cooked rice and finishes under dum to marry the flavors. Kachchi is harder to execute because the meat has to be perfectly marinated to cook through in the dum window.