Neither one first. The real question is which of your two pains costs more every month. How to calculate it, and the decision rule.
An owner calls and says: we're torn between an ERP and a CRM. Nine times out of ten the question doesn't work in those terms. It works like this: which of my two pains costs me more every month? Because the two systems don't solve the same problem, and neither solves the other's.
The useful distinction.
An ERP handles what has happened. An order is signed: invoice it, decrement stock, book it, pay a supplier. It's the company's record of truth. A CRM handles what might happen: where is this prospect, who follows up, when, and what are the odds they sign this quarter. It's a forecasting instrument.
A CRM contains false data by nature. An opportunity at 40% probability doesn't exist yet.●
An ERP contains only facts. Two different regimes of truth — which is why merging them without thinking produces dashboards nobody believes.
The question to ask instead.
Take a sheet of paper and put a number on two amounts over the last quarter. The cost of the operations pain: hours spent re-entering the same data in two tools, times the loaded hourly rate, plus the billing errors you found, plus stockouts or overstock, plus month-end close beyond what's reasonable.
The cost of the revenue pain: opportunities lost for want of follow-up, plus the gap between your forecasts and your actuals over three quarters, plus the time a salesperson spends reconstructing an account's history before a call. The larger of the two names your first project. That's not intuition, it's subtraction.
Three cases where the answer is already known.
You have inventory, production or billable projects: start with the ERP. Those three produce errors that cost money immediately — wrong stock is paid for in unnecessary purchasing, a badly tracked project in unbilled hours.
You sell a service and your pipeline lives in people's heads: start with the CRM. There's nothing to integrate, value lands in six weeks, and you get a forecast usable by a bank or a board.
You're under ten people: start with neither. A disciplined spreadsheet with a single source of truth will take you further than a system nobody has time to feed. The tipping point isn't a company size: it's the moment two people give you two different numbers for the same question.
The most expensive mistake.
Wanting both at once. An ERP rollout and a CRM rollout draw on the same people — leadership, finance, the ones who know the processes — and those people already have full-time jobs. Running both guarantees both are badly configured and neither is adopted.
Do one, let it live a quarter, then start the second knowing at last which data has to flow between them. You'll design the integration from an observed need rather than an assumption.
What we never recommend.
An ERP chosen before the processes are mapped: the tool doesn't reveal your processes, it freezes them, and freezing a misunderstood process costs more than having no tool. A CRM imposed as a way to monitor salespeople: the team stops filling it in within six weeks, the data goes false, and a false forecast is worse than no forecast. And a module configured with no named user: if nobody can say who will use it on Monday morning, it serves nothing.