The Minus K BM-1 has 0.5 Hz Horizontal and Vertical resonance, whereas the BM-6 has higher resonance frequencies. The BM-6 is like an air table (but without the air). The BM-1 is unlike anything else when it comes to isolation, outperforming pretty much everything.
Rumor has it that Minus K has a low profile model with 0.5 Hz Horiz/Vert in the works. But I imagine the payloads will be insufficient for the Walker.