A spreadsheet catches the leak you already suspect. Purpose-built job costing catches the one you don't. That's the whole comparison in a sentence, and everything below is just the tradeoffs behind it.
Most contractors I know run margin off a spreadsheet, and honestly it works longer than software vendors want you to believe. If you're doing under 20 jobs a year and you personally touched every one of them, a spreadsheet isn't a compromise—it's the correct tool. You know where the numbers come from because you typed them in. That's not nothing.
What a spreadsheet is actually good at
Zero cost. Zero learning curve. Full control—no vendor deciding how a change order should be categorized. And it shows you exactly the numbers you built it to show you.
That last point is the trap. A spreadsheet is a mirror. It reflects the assumptions you already have. If you never thought to track labor burden separately from base wage, the sheet won't flag it. If your material waste is quietly running 12% over estimate, the sheet shows you the total you plugged in, not the variance you never calculated. You audit what you already audit. The leaks you'd never think to check stay invisible because nothing is checking for them.
The spreadsheet never lied to me. It just never told me the thing I didn't ask.— remodeling GC, ~$2M/yr, after switching
What purpose-built job costing actually buys you
It buys you variance you didn't request. Committed-cost tracking, so a PO that's issued but not yet invoiced still hits your job number today instead of surprising you next month. Labor feeding in from time tracking instead of a memory-based number at week's end. Real per-phase margin instead of one blended project number that hides a bathroom losing money inside a kitchen that carried it.
Here's the honest catch, and it's the whole catch: job costing software is only as good as what feeds it. If your crew's hours still land in a text message, if material receipts still live in a truck console, if your payment data lives in a separate world entirely—the software gives you a very expensive, very polished version of the same blind spots. Garbage in, dashboard out. The tool doesn't fix your inputs. It just makes bad inputs look official.
The all-in-one vs. best-of-breed question underneath it
The tempting fix is one platform that does everything—estimating, costing, scheduling, invoicing, payments. One login, one throat to choke. The tradeoff is you inherit that vendor's opinion of how your business runs, and you're locked in the day you outsource your whole operation to it.
The approach I'd argue for: keep the pieces that are specific to how you run—your estimating logic, your phase codes, your labor rules—tailored and in-house, in tools you control. Then bring in a third party only for the one function that genuinely benefits from a neutral outside party.
That function is where the money changes hands. Job costing tells you your margin is right. Payment protection makes sure you actually collect it. You don't want your own stack refereeing a payment dispute with a client—that's the one seat where a neutral third party earns its keep. Escrow is the piece that shouldn't be in-house, precisely because its whole value is that it isn't you.
Where this leaves you
Run the spreadsheet as long as it's honest with you. Move to purpose-built costing the moment your jobs outgrow your memory—and only after your labor, material, and payment data actually flow into it, because before that you're paying for a nicer mirror.
And wherever your costing lives, keep the money-changing-hands part out of your own stack. That's the one place neutral beats tailored, every time. If you're mapping out which pieces stay in-house and which one shouldn't, that's the right time to see how the escrow piece fits.