Revenue churn divides MRR or ARR lost to cancellations and contraction by the starting recurring revenue. It's the most direct measure of how leaky the bucket is. Revenue churn ignores new sales and expansion, it's the pure 'how much are we losing' number.
The relationship between revenue churn and logo churn reveals customer concentration. High revenue churn with low logo churn means a few large accounts are leaving; low revenue churn with high logo churn means many small accounts are leaving but the big ones are sticky.