Game mode doesn't matter, it's worse fps period.

Two 1.6.4 pictures, three 1.7.2 pictures taken in a 100% void world for maximum results.

1.6.4 (1) = Absolute minimum video settings (standard size windowed mode) Average 220fps
1.6.4 (2) = Absolute maximum video settings (full screen) Average 70fps
1.7.2 (1) = Absolute minimum video settings (standard size windowed mode) Average 65fps
1.7.2 (2) = Max video settings minus anisotropic filtering and mipmapping (full screen) Average 5fps
1.7.2 (3) = Absolute max video settings (full screen) Average 8fps

All pics taken immediately after changing settings. Averages taken across 60-80+ second increments of time.