Independent comparison for enterprise buyers. Updated May 2026.
Quick verdict: Choose Deloitte for the largest Big Four consulting practice by workforce and revenue, particularly strong technology delivery across SAP, Oracle, Workday, Salesforce, and ServiceNow at very large scale. Choose EY when audit-rooted advisory must coordinate closely with tax transformation, transactions, or supply chain restructuring, when SAP and Microsoft alliances anchor the programme, or when the buying preference favours a firm that retained a unified audit-and-advisory model after pausing its 2023 separation plan. The differentiator is consulting scale: Deloitte is materially larger; EY is comparable on advisory breadth but smaller on pure technology delivery.
| Criteria | Deloitte | EY |
|---|---|---|
| Editorial score | 4.3 / 5.0 | 4.1 / 5.0 |
| Heritage | Big Four professional services | Big Four professional services |
| Workforce | ~470,000+ globally | ~395,000+ globally |
| Revenue (FY) | ~$67B+ (network) | ~$51B+ (network) |
| Key Strength | Largest Big Four consulting practice; technology delivery scale | Tax and transactions advisory; SAP alliance depth |
| Ecosystem / Partner Network | SAP, Oracle, Workday, Salesforce, ServiceNow | SAP, Microsoft, ServiceNow, IBM, Salesforce |
| Geographic Reach | 150+ countries | 150+ countries |
| Key Limitation | Independence rules restrict audit-client work | Smaller pure technology delivery practice; post-Everest restructuring noise |
Deloitte and EY are two of the Big Four professional services networks. Both operate as global member-firm structures, deliver audit, tax, advisory, and consulting services, and field substantial technology consulting practices. The two firms are direct competitors on most Big Four advisory engagements, particularly across large enterprise transformations and regulated industries.
Deloitte is the largest of the Big Four by network revenue (approximately $67B) and consulting practice size. Deloitte Consulting fields some of the largest SAP, Oracle, Workday, Salesforce, and ServiceNow practices in the industry and competes head-to-head with Accenture on the largest platform programmes. Risk and Financial Advisory, Tax, and Human Capital service lines integrate with the consulting practice on coordinated transformation.
EY is approximately $51B in network revenue with around 395,000 people. EY's heritage is audit and tax, with particular strength in transactions advisory, working capital optimisation, and supply chain advisory. EY paused its planned 2023 separation of audit and consulting (Project Everest), retaining the unified Big Four model. EY has strong SAP and Microsoft alliances, with notable depth in SAP S/4HANA tax-led transformation and intelligent automation through its EY.ai platform.
On generative AI, both firms have committed multi-billion dollar investments. Deloitte has launched Project Apollo and the Deloitte AI Institute. EY launched EY.ai with a $1.4B+ investment in 2023, embedding generative AI across audit, tax, and consulting services and offering enterprise AI advisory and delivery to clients. Both firms emphasise responsible AI and governance.
On industry depth, both firms have broad sector coverage. Deloitte is particularly strong in public sector, financial services, life sciences, and technology. EY has comparable financial services depth, leading capability in tax and transactions, strong presence in private equity advisory, and growing strength in supply chain and operations transformation.
Both firms operate at premium Big Four rates with broadly similar bands. Senior partner rates typically range $450-720 per hour, senior managers $260-460, consultants $160-310, and offshore delivery rates $50-130 depending on geography. List pricing as of 2026; figures shown are pre-discount on enterprise master service agreements. Both use blended rate cards on large fixed-price work and value-based pricing on advisory mandates.
Typical fee profile for a large SAP S/4HANA programme: $25M-90M+ for Deloitte, $20M-75M+ for EY depending on scope. Tax transformation and BEPS Pillar Two compliance programmes: $3M-15M, where EY frequently leads on competitive bids. Transactions advisory mandates: $1M-10M. Competitive bids between the two firms typically land within 10-15% of each other. The primary buying-side caveat remains auditor independence: if the buyer uses either firm as external auditor, consulting work will be restricted and may force selection of the alternative.
Choose Deloitte when the programme is large-scale technology delivery requiring substantial workforce throughput, when SAP, Workday, Salesforce or ServiceNow at enterprise scale anchors the work, when integrated risk, tax, or human capital advisory must coordinate with technology delivery, or when the buying preference favours the largest Big Four consulting practice. Deloitte typically wins where the buyer wants Big Four advisory positioning combined with delivery scale comparable to the large technology services firms under a single accountable lead.
Choose EY when audit-rooted advisory must coordinate with tax transformation, transactions, or supply chain restructuring, when SAP and Microsoft alliances and EY's tax-led S/4HANA transformation patterns are decisive, when BEPS Pillar Two and global tax compliance technology are central, or when private equity portfolio value creation services are in scope. EY also tends to win where the buyer prefers a more advisory-led, partner-fronted engagement with deep tax and transactions integration.
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