My experience has been that the .204 Ruger is a side step from the .223rem, or even a step down. The .204R does handle smaller bullets better than the .223rem, or at least it's easier to find lighter bullet factory rounds, which some guys consider to be a benefit in terms of pelt-friendliness.
There's a breaking point for me below 45-50grns where you'll start seeing better pelt-friendliness, but more run aways. I have more run-aways with a .204 than a .223rem.
Frankly, it's a joke to say that the trajectory of the .204R is really worth much. By the time it matters (i.e. you're outside of 300yrds), then either one is marginal, and the heavier bullets of the .223rem will keep it trucking further than the .204R. To each their own, I have both, like both, but I'd give up the .204R, I won't give up my .223rems.