Both are critical. Through measuring sales churn and customer churn, a company can determine if retention is consistent across the customer base, whether there is more turnover with small customers (higher customer churn, lower revenue churn), or if large customers are more at-risk (lower customer churn, higher revenue churn). By having several ways to quantify overall consumer health, a company may avoid over-reliance on a single metric and be more likely to find problems in the data before they become a problem.
