RE: .204 or .25 WSSM?
When comparing the 204 to anything else you need to compare both using not equal bullet weights But bullets of equal sectional density. The forty grain 204 bullets sectional density is higher than the same weight in a 22 caliber bullet because the 204 is smaller in size. This is not to say that the 204 is not the better pelt cartridge as its the same principle as the old 17 Remington. The 243 is a good varmit caliber as would the 25-06 or 25WSSM. However pelt damage is bound to be more of a concern with the bigger calibers. Myself I use the 223.