My 223 & my 204 are both 1:12 twist. I shoot hornady 40 grain vmax out of both. The similarities in the setups are so much that I don't think you could find a better comparison between the two calibers. I will tell you this: the difference in muzzle velocity & performance is imperceptible. Recoil, muzzle blast, & muzzle velocity are all very similar. In addition to all of this, I choose to shoot my 223 most often because I have a ton of once fired brass & the bullets are cheaper.
My suggestion for a varmint rifle would be a slow twist 223 and light bullets if cost per round is a big concern. If its not as much of a concern and muzzle velocity is what you really want, shoot those same 40 grain pills out of a 22-250 and see how that works for you.
My suggestion for a varmint rifle would be a slow twist 223 and light bullets if cost per round is a big concern. If its not as much of a concern and muzzle velocity is what you really want, shoot those same 40 grain pills out of a 22-250 and see how that works for you.