I got both.
both are excellent tyres.
UC6 is more soft and has better road grip and braking.
CC6 is a bit hard but has better durability and rolling resistance (better fuel economy).
noise levels are same which is excellent for both.
Overall I think UC6 is better more premium tyre while CC6 is a budget option meant for hatchbacks and compact sedans.
UC6 starts from 16" and CC6 starts from 15"