I had a C20 for thirty years -- has very nearly the same circuit as the C22. Also owned an ARC for a few years, but it was an LS17. I agree with Jaybo that they are both more neutral than the cj's or many other vintage pre's. To my ears, the mac was more euphonic, and easier to listen to, but probably less transparent (or maybe it was just aging).
Just another data point. Given the choice, I'd go for the Mac, but I like the Mac house sound more than I like the ARC house sound.
HTH
Just another data point. Given the choice, I'd go for the Mac, but I like the Mac house sound more than I like the ARC house sound.
HTH