Short answer: No, it's irrelevant.
Pretty much all upper-tier and most mid-tier sets have 3D. So your premise is true only in the sense that you'd probably be comparing one to a lower-tier non 3D TV.
The exceptions are getting hard to find, it seems to me. Sharp still offers a mid-tier non-3D set, the 650U, for instance.
I bought a 65" LG 65LW6500 passive 3D set about a year and a half ago. Then a Sharp 70" 640U (the 650's predecessor), a month ago. The Sharp has a noticeably better native contrast ratio (2,200:1 vs 1,600:1) than the LG, and without going into further detail, overall a better picture, IMO.
I confess I got the (non-3D) Sharp mainly for the matte screen, since the LG is a real mirror, and has been relegated to the living room. Since Sharp 3D TVs are active 3D only, I passed on the step-up models, due to my dislike of active.
Please pardon the long-winded response.
Good luck whatever you get.