One direction, one trigger, one source of truth for the contract. The quote generates the contract record, the contract drives billing, and billing never writes commercial terms back into the CRM. Two systems both authoring subscription values is the fastest way to an unreconcilable book.
Pricing model decides the billing side: flat-rate subscription work is well served by standard tooling, while consumption billing needs metering. Among companies that bill on consumption, virtually all meter usage but only about 20% run a purpose-built metering engine — the rest meter through the warehouse and Stripe.
Every claim above comes from work LeanScale published. These are the sources.