I'd probably pick a .223 for one all-around varmint centerfire too--if I had to! Have found the standard .223 will get within 50 fps of the AI if loaded up to the same apparent pressure, where "pressure signs" don't appear. But do like the AI feature of not having to trim brass much, if at all.
For just small-rodent shooting, however, I'd be pretty happy with the .17 Hornet, and ground squirrels and PD's are the only varmints I shoot in most years. Some people do have trouble handling the tiny bullets when handloading, but I only drop a few--and find them again anyway after my periodic sweeping of the loading room. The cases do require trimming after a few firings, even when neck-sized only, but I have a Gracey trimmer than zips through them quickly, trimming and chamfering around 20-25 cases a minute. But who knows? Maybe next year somebody will introduce another small rodent round, and I'll be as fickle as a typical rifle loony.
