I have two sequences: one is coding (A) and one is non-coding (B). I calculated selective pressure for A using Nei-Gojobori method and Wong-Nielsen for B, respectively. Let's assume I get ζ=0.3 for B and ω=0.5 for A. The question is, can I compare ζ and ω, saying that purifying selection on sequence B stronger than A's? WN method is a modification of NG so both parameters seems equal, in my opinion.