If there are two antennas of 50 Ω and 377 Ω (same as the intrinsic impedance of air) impedance with 0 $\Omega$ ohmic resistance, and they are exactly matched with their transmission line, then which antenna is more effective in terms of radiating R.F. power into space? 

That is, if both antennas have VSWR = 1:1, then which one is more efficient? 

Note: that the term 'efficiency' in above, does not mean the definition of antenna-efficiency. I know that antenna-efficiency is 100%, since there are ZERO ohmic loss and $\infty$ return-loss. So, from "efficient", I mean the effectiveness of the antenna in radiating energy in space.