Which acoustic panels absorb the most noise?
What are you trying to achieve? Are you just looking to tame reflections in a live room, or are you looking for complete isolation of sound entering or leaving a given space?
If it’s the latter, then acoustic panels will NOT do the job on their own. You ideally want to add mass to the walls. Mass (or density) is what will prevent sound from moving through walls (either inbound or outbound).
The scientific parameter in acoustics which deals with the sound absorption capacity of a material is NRC- Noise Reduction Coefficient.
Its value ranges from 0 to 1 where 0 is no sound absorption at all (completely sound reflecting like glass, concrete) and 1 is all the sound incident on the material surface is absorbed (like perfect black body in lighting).
So ask any manufacturer or vendor for the NRC value, which is a number between 0 & 1 (eg-0.2, 0.66, 0.95, and 0.36). Higher the number higher is the sound absorption capacity of that material and vice versa.