I would vouch for the 243, but just remember that factory barrel twist rates and ammo choices are not optimal. I started out with a Savage 12 243 Win, shooting 95gr Hornady SST ammo (I believe it was the superformance brand). It did alright, this is a 26" varmint barrel with a 1:9.25 twist rate. Certainly a dramatic change in lethality and ballistics compared to a 223. The wind drift on the 95gr SST leaves all the regular 223 bullets in the shade... Close shots were at 130 yards on coyote, long was 250-350 yards - about as far as it gets on the property accessible to me.
I then re-barreled it to a 243 AI, Shilen 1:8 26" varmint barrel. Loaded my own ammo, 95gr hunting Berger VLD over 41gr of H100V powder. Based on drop data, this load is running close to 3200fps and is the load I use for fireforming/hunting. (Hornady claims 3185fps for the superformance load from a 24" barrel) Once I work up a decent size batch of brass, I will make serious work of my 105gr VLD load.