You bring up an excellent point, I had neglected to show the effect of time in my explanation as you said. And it is true that this has real impact as to the magnitude of what I was talking about. But so long as the switching time != infinity, the power consumed is not equal. Using your example,

1 Ohm Case : P_res = integral exp(-2t) from 0 to tao -> .4323J 1/2 Ohm Case : P_res = integral 2*exp(-4t) from 0 to tao -> .4908J

Of course the effect diminishes greatly (to zero as you showed) as the switching time increases. But we are dealing with a great number of transistors switching very many times so the effect is still noticeable given timings are tight enough.

The thought on power savings as you mention is interesting but i am unsure off the top of my head of it.