Among professionals, the general consensus is that they are both involved in 100% of the generation of lift, and if one was lacking nothing would happen. Even initiating the discussion about which one is "the strongest" implies having taken a wrong turn somewhere in the maze of theories, I'm afraid. It's a chicken or egg discussion, in a setting where it is known that both the chicken and the egg have existed since the start of time.
The reaction from the downward displacement of mass is exactly as much as the pressure gradient will cause, and the pressure gradient is exactly that which corresponds to the downward displacement of mass.
The one caveat would be that Bernoulli's theorem is invalidated as compressibility builds up to be a significant factor.