223 is great as there is quite a few factory guns that have either a 1:8 or 1:9 barrel twist, which allows you to shoot somewhere between 40gr and 75gr bullets.
Which means the same gun can be used with super fast varmint loads but also medium/small game loads, and high BC target loads.
22-250 and 204 Ruger might be better as varmint rounds, but very few factory guns can shoot the heavier bullets.
Also you can get an AR15 with a Wylde chamber and shoot dirt cheap 5.56 ammo for plinking, and with the same gun shoot sub MOA target loads.
And its cheap for reloading components, easy on barrels and ammo is very plentiful.
I quite like 223.
