The Cascade Equivalence Hypothesis: When Do Speech LLMs Behave Like ASR$\rightarrow$LLM Pipelines?

Research reveals that speech LLMs don't perform significantly better than traditional ASR→LLM pipelines in most deployed scenarios. The study shows speech LLMs essentially function as expensive cascades that perform worse under noisy conditions, with advantages reversing by up to 7.6% at 0dB noise levels.