The short answer
Choose by what the contract and the client programme office require, then by who will maintain the schedule, then by scale. Neither tool is better in general. A well-kept Microsoft Project schedule beats a badly kept P6 one, and a schedule that the Scope requires in P6 format cannot be supplied in anything else. The usual mistake is applying the wrong tool: P6 where Microsoft Project would have done, or Microsoft Project where the client expected XER files.
Where Primavera P6 is stronger
P6 is built around a central database that many people use at once. Enterprise project structure, activity codes, global change, shared calendars and a role and resource structure that spans projects are core features. On a programme with several contractors and shared resource pools, that structure is the main reason to choose it.
Baselines: P6 lets you assign a project baseline to compare against and keep several for different purposes (contract, approved change, forecast). That suits a contract where each update is compared to the last accepted programme.
Exchange: large clients and their programme offices commonly ask for XER files, and most schedule-analysis tools read XER directly. Where the Scope or the client's programme requirements name P6 or XER, that settles the question. Read those documents; sector custom is not a requirement.
Cost integration: Oracle's cost and controls products sit in Primavera Unifier and Primavera Cloud, and P6 data is regularly fed to third-party cost and EVM platforms. How sound the link is depends on how it was built and who maintains it.
Where Microsoft Project is stronger
Familiarity: a project manager who is not a trained planner can maintain a Microsoft Project schedule at a basic level. P6 needs training, and errors such as a damaged WBS or broken resource assignments take longer to find and repair.
Microsoft 365 fit: Planner premium plans, Teams, SharePoint and Power BI sit in the same environment. Where portfolio reporting already runs there, a Microsoft scheduling tool adds less integration work. Viewing has friction either way: a full .mpp file needs Project and an XER needs P6 or a viewer, so most reviewers receive a PDF or export.
Microsoft licensing after Project Online (as at October 2026)
Project Online was retired on 30 September 2026. Project for the web now sits inside Planner as premium plans. For scheduling work you now choose between Planner Plan 1, Project Plan 3, Project Plan 5, or a perpetual desktop licence (Project Standard or Project Professional). Check Microsoft's current licensing pages for contents and price before budgeting.
Standard Microsoft 365 business plans do not include scheduling-grade Project. Treat it as a separate licence cost.
For P6, Oracle sells by licence model and prices come by quotation, so no figure is given here. Compare quotes on the same users, period and support terms.
Other tools worth knowing
Oracle Primavera Cloud is Oracle's hosted scheduling and portfolio product. Ask whether the client accepts XER files or requires submission through it.
Asta Powerproject is used by some UK contractors. If a team schedules in Asta, test the export to the client's format on a real programme first, because logic and calendars can change.
NEC4 programme duties and the tool
Neither tool is required by NEC4. Clause 31.2 lists what the first programme must show, including planned Completion, key dates, the order and timing of operations, float, time risk allowances and the principal resources. The Scope and Contract Data add specifics such as logic detail or file format. Either tool can meet clause 31.2 if the Scope allows it.
Clause 32.2 sets when revised programmes are submitted: at the Contract Data intervals, when instructed, and when the Contractor chooses. The interval is a contract term, not a monthly default. Compensation event quotations carry a revised programme where the event affects the programme (clause 62.2).
Worked example. The Accepted Programme shows planned Completion on Friday 8 October 2027. A compensation event delays a critical activity by 15 working days. In P6, copy the accepted version, insert the event's fragnet, reschedule and compare to the accepted baseline. Planned Completion moves to Friday 29 October 2027: three weeks, or 15 working days with no bank holidays in the period. The Contractor includes that revised programme with the quotation. The Project Manager checks the logic and the dates. The same exercise works in Microsoft Project if the accepted baseline has been saved.
What matters more than the tool
The 14 DCMA checks are tool-neutral. They are widely used in UK practice; National Highways, Network Rail and HS2 do not mandate them. Microsoft Project schedules can be tested equally well, usually after an export. Hard date constraints make either schedule look tidy while it fails to respond to change.
On a QSRA we need a logic-driven model with credible durations and calendars. A clean schedule in either format can be risk-analysed; a constrained one needs repair first.
Decision rule by programme type
Step 1: read the Scope, programme requirements and any client PMO instructions. If they name P6 or XER, use P6. If they say nothing, go to step 2.
Step 2: apply the SOMA rule of thumb, which is a judgement and not a standard. Below about £10m, one contractor, one project and a project manager maintaining the schedule: Microsoft Project. Above about £20m, several contractors or packages, shared resources or an integrated cost-schedule control regime: P6, or Primavera Cloud if the client uses it.
Step 3: between about £10m and £20m, decide on three things: who will maintain the schedule (trained planner or project manager), whether the client PMO exchanges XER, and whether the programme feeds a cost or EVM system. Two or more answers pointing to P6 means P6.
Use both only when there is a reason: P6 as the controls master and a summary export for executive reporting. Board packs are usually built in PowerPoint, Excel or Power BI, not a second scheduling tool.
Do not choose by what the planning team prefers. A planner who insists on Microsoft Project where the Scope requires P6 creates a compliance problem. A client that mandates P6 for a £2m single-contract refurbishment creates overhead the control benefit does not repay.