Just mempool. Knots users store the exact same chain and validate the exact same blocks as core users. And yeah, when spam is low not a big deal. During spam rushes where spam is paying 600s/vbyte you run a real risk of getting robbed for a lightning justice transaction by filtering your mempool when no one else does. Every knots person I asked if they were willing to fork chains over it said no. The quiet part there is that they are just virtue signaling then. Luke's shenanigans like begging poverty to the community then losing 100 coins from a hot wallet and blaming core devs are a whole different issue. They are an issue for sure. I still mine with ocean for my pool mining but I use the no filter endpoint to do it.