I went from a V20 to a V20c. No regrets, but...
* The V20c is not much lighter, and that includes the front end. The carbon pieces are cool, more aero and modern looking. But these parts are also pretty beefy, which I imagine is a demand of the frameset design itself. I remember an older thread where people were asking when CB was going to release a full carbon V, and Robert finally came on and said that the design would require so much carbon to support the forces it receives that the bike would gain weight over the aluminum version. In brief, don't let the minimal weight savings be the only reason to upgrade to the V20c.
However...
* The V20c does feel a bit more planted and connected to the road. It has a smoother ride and it carves corners well. Not that it rides all that much different than the V20, but there is a more solid and polished quality to the V20c's ride, probably having to do with the carbon front end, and maybe the thru-axles.
* The V20c is routinely about 1 mph faster than the V20. I cannot decide if that difference sounds like a lot, or very little, but sure, I'll take it. I had the shortest chainstay on the V20, but the V20c does not offer a shorter chainstay than what comes standard, so my feet ended up being three inches higher, which has fortunately worked out fine. That three inch lift alone could account for much of that small speed boost.
* the V20c's carbon bits do look pretty damn sexy.
My V20 was actually a 2015 V.2 that eventually took on the V20 boom and chainstay, effectively making it a V20. Still, the bike was eight years old, with many miles on it, and when the V20c was coming, I figured it was time. If I had a two or three year old V20, it would have been a harder decision. I love my V20c, but knowing what I know now, the older V20 is still a damn good bike. The V20c does not outshine it by much.