The C is punchier, bolder, more extended in the low end, tighter and faster, but still far from really being a tight amp without a boost. The lead tone is even a bit more liquid and complex/nuanced. For leads I liked the D almost as much as my iic+ and prefer my C by a little to my iic+ for leads. To me those are the main benefits I got with my C vs D
In terms of the overall voicing itself (I guess what would show more in a recording context) I thought they were very close. The main difference is the C is a bit more aggressive in the upper frequencies, but less rich sounding in the low mids vs the D. This is the one thing I preferred about the D. The goofy way I like to describe it is playing powerchords on the D reminds me a bit of Coca Cola from the richer low mids, while the C is more like Pepsi and the Rev F and G are maybe like stale coke hahaha, the 3ch’s and MW’s would be even more stale coke. My Rev 1 Uber would be cream soda and some of Marshall’s or modded Marshall’s would be sprite