[W126 Coupe] tire weights

[Shayegan, Richard]

I'm deciding between Sumitomo HTR 200's and Firestone Affinty LH-30's (my only choices in 205/70 if I need H rated or better - in this case H - unless I want to spring $225 or $379 per tire for Michelin XDX or XWX's). The sumitomo is marketed more in the area of performance, but it's also 2.5 lbs (19 vs 21.5) heavier than the Firestones. Is that enough dead rotating mass to make a difference?
Richard