Comparing KASAN with slub_debug there is one type of bugs that can be caught by slub_debug, but not by KASAN.
If freed object or redzone is overwritten by something that's not instrumented with KASAN (uncommon asm, DMA, VM guest), then KASAN won't catch it, while slub_debug still can catch it later (with no access stack, but still).
To achieve full parity we could fill object/redzone with a pattern and check that it's not overwritten when the object is evicted from quarantine. We will still have alloc/free stacks + quarantine gives better detection for UAFs.
But not sure how frequent are such bugs.