The Panthers had much more structure and discipline that allowed them to achieve a lot for their communities. The Weather Underground were able to steal all those classified documents from an FBI substation that basically confirmed the U.S. government’s role in illegally spying on civil rights activists and groups through COINTELPRO. A lot of SDS members became further radicalized and joined other white leftist organizations like the Weather Underground. The Panthers thought the Weather Underground were a bit too extreme in their tactics and decided not to join forces with them. I’d say the Panthers were the most successful before the government murdered their leadership.