I second the .223. A lot cheaper to reload. It might not have the terminal balistics of the hotter or larger calibers, but it kills em good and dead.
Of course since I started my varmint career using my Remington 700 VS in .308 using 110 gr. V-Max, nothing has the terminal balistics to compare. I do know my 50 gr. loads for my .223 take at least half as much Winchester 748 as the 110 gr. .308 loads.
The .204 and the .22-250 of course won't take that much, but the more money you save, the more you can shoot, the more fun!