I really like my .204 as a dedicated varmint rifle. Less recoil, less muzzle blast, shoots like a laser to 400yds and I find factory ammunition readily available. I load for mine so, my ammo is cheaper but, I don't think factory ammo price is scary.
.223 is a fine cartridge, if you like to shoot FMJ it can be cheaper I guess. I like the ballistics of the .204 better. The .223 can be used for deer so, maybe its more versatile. I wanted a dedicated varmint rifle and found the .204 to be just what I wanted. I wouldn't trade mine for a .223 of any kind. The first rifle I bought for my son was a .223. He killed his first deer and his first coyote with it. It performs flawlessly if he does his part. I think I can out shoot him with my .204...........maybe?