I've heard that the M-1 is very similar to a Holley Strip Dominator.
When I had a W-2 set-up in my old bracket Challenger, I found that the Edelbrock Victor had a deeper plenum than the Holley Strip Dominator for the W-2 heads. I would guess that the same would be true for the standard head versions and could explain why the Holley may have a little more torque at lower rpms. But I've never seen a comparison on paper or on a dyno nor tried to make a back-to-back comparison back then. But I usually ran the Holley with very satisfying results.