I bought my first CU24 in 1991. I also had a 1993 Artist II, which was the precursor to the CU22, and quite a few CU22 models throughout the 00s. All were very nice, but none were what they are now. So I voted "new."
First of all, I like the thinner V12 finish (both for look and feel, and while I'm unsure finish affects the tone, I think the newer ones sound better), plus I think that all the other little tweaks to the guitars have resulted in significant improvements to the tone. From the nut, to the sustain, to the liveliness, to the materials, to the tone controls, to the switching, the guitars are simply better sounding (to me, usual disclaimers apply).
Just playing the guitars clean shows a big improvement and in my experience, better ability to hear the guitars' woody resonances. I have recorded my PRSes from Day One with them in my ad work, so I am very, very familiar with recorded tones, and I often take a direct feed from the guitar to re-amp later.
I used to have the urge to swap out pickups before the 57/xx series came in. That has changed, and in my opinion, much to the better. But you can still buy new ones with the older style pickups.
I am one who agrees that the rotary looks nice, but it's an ergonomic nightmare, and I never thought it was a useful solution. The toggle was better, with a pull-up, but even that is a bit fussy, and not as fast and sure as the blade switch.
Neck carves to me are six of one, half dozen of the other. Took me ten seconds to get acclimated to the new carves.
As to the tuning machines, I find the new ones are very accurate and stable. My #1 is a 2011 Artist V, which is a fancy CU22 for all intents and purposes. And it's the single best sounding guitar I have ever played. I doubt the tuning machines affect tone, but the new ones are kind of pretty.
I get peoples' attachment to older ones, and that they like what they're used to, but there is simply no tone comparison between, say, my 2006 CU22, or my 2003 CU22 Artist, or even my '93 Artist II, and what they're making today. The new ones are terrific guitars. And in general, I prefer them to the old ones. That said, you can find a killer older one, and probably find a new one that isn't as good, but I'm saying on average, I prefer the new ones.
BUT -- the bottom line is what you, the prospective owner, dig. And that's going to vary from person to person and can't be argued with. One can only express a personal opinion.