Punisher,
I took a peek at your info and I see your from Michigan. So, I'm gonna assume that is where you do your varmit hunting. So, varmits like priarie dogs are not in your life. But groundhogs, crows, maybe fox and such are.
That being said I will tell you that I shoot the 223 from my Contender with a 24" barrel. The 223 has no problem with fat groundhogs out to 400 yards using 40 grain Nosler balistic tip bullets at maximum loads. (That's about 3600fps mv).
Now, the 204 ruger (which I have no experience with) is suppose to be an excellent varmit bullet as well. It has speed on it's side (I think 4000fps or better) which always helps in exploding small furry things. From what I've read it is as accurate as anything.
So there, that's a big help. I will say that I'm not rushing out to get a 204 Ruger barrel. Heck, I'm not even walking out to get one. I love my 223. If I were "starting over".....I dunno....I would say do more research....like your doing now. Then decide.
I will say that I hunt with a buddy that shoots a 22-250. And for what we hunt, (Groundhogs and smaller) the 223 does everything the 22-250 does. (Now remember...I am qualifying it for Groundhogs and smaller!!!!). Also, the 22-250 will give you on average 500fps faster speed for every grain weight of bullet over the 223, but it will also take an average of 10 grains of powder per shell to do this. Now, that's probably not a big deal, but dead is dead to a groundhog.....even when it cost less to do it.
Dave.