Microsoft Sentinel vs Splunk for Managed Security

Microsoft Sentinel and Splunk Enterprise Security are both SIEMs: they collect logs, correlate them into alerts and keep them for investigations and audits. Sentinel is Microsoft's cloud SIEM, billed per gigabyte through Azure with Office 365 audit logs and Microsoft Defender alerts free to ingest, which makes it the simpler start for a business that runs on Microsoft 365. Splunk runs as a cloud service or in your own data center, prices by ingest, workload or activity through a quote, and suits organizations with large, varied data and people who already know it.

Neither is SentinelOne, a separate endpoint security company covered below. If you are still deciding whether you need a SIEM at all, start with XDR vs SIEM for small business; for how a SIEM pairs with automation, see SIEM vs SOAR.

What is the difference between Microsoft Sentinel and Splunk?

How does each one price your data?

Sentinel publishes its prices. Microsoft's list price for the analytics tier in the East US region is $4.30 per GB on pay-as-you-go, as of October 2026. Commitment tiers start at 100 GB a day, listed at $296 a day or about $2.96 per GB, and Microsoft's Sentinel pricing page puts the savings over pay-as-you-go at up to 52%. A 50 GB a day tier is in preview with promotional pricing through December 31, 2026. Data you only need to keep can go to the data lake tier, listed at $0.05 per GB to ingest plus $0.10 per GB to process, and $0.026 per GB per month to store, measured after Microsoft's standard 6 to 1 compression.

Several details lower a Microsoft shop's bill. According to Microsoft's billing guide, Azure Activity logs, Office 365 audit logs and alerts from the Defender products are free to ingest; the first 90 days of retention cost nothing; and a 31-day trial covers 10 GB a day. Customers with Microsoft 365 E5 and the other enterprise licenses Microsoft lists also get a data grant of up to 5 MB per user per day for Entra ID sign-in and audit logs and some other Microsoft 365 data. Business Premium is not on that list.

Splunk does not publish Enterprise Security prices. Its pricing page offers activity-based, workload or ingest pricing and asks you to request a quote, and it counts eligible Cisco telemetry at a weighted ingest rate of 50%.

An illustrative calculation: a 60-person firm sending 3 GB a day of paid logs, such as firewall and Entra ID sign-in data, to Sentinel on pay-as-you-go would spend about $387 a month at the East US list price (3 GB times $4.30 times 30 days), before any free sources. A Splunk quote for the same volume depends on the pricing model you choose.

Is Microsoft Sentinel the same as SentinelOne?

No. Microsoft Sentinel is Microsoft's SIEM. SentinelOne is a separate company whose core products are endpoint protection and XDR under the Singularity name, and it also sells its own SIEM, Singularity AI SIEM. Comparing them usually means comparing a log platform with an endpoint platform, and a business can run both: SentinelOne says its Cloud Funnel can copy its endpoint data into a customer-owned SIEM, and Sentinel accepts outside products through connectors, Syslog, CEF and REST APIs.

Is Azure Sentinel the same as Microsoft Sentinel?

Yes. Azure Sentinel was the product's earlier name; Microsoft's old Azure Sentinel pricing address now redirects permanently to the Microsoft Sentinel page, and the documentation still sits under Azure paths on Microsoft Learn. The bigger change for current users is the portal. Microsoft says that after March 31, 2027, Sentinel will no longer be supported in the Azure portal and will be available only in the Microsoft Defender portal, where it is already generally available, including for customers without Defender XDR or an E5 license.

What does it take to run each?

Either SIEM is only as good as its connected sources and its rules. Expect the same work on both: decide which logs matter, connect them, write or tune detection rules, set retention, and make sure someone reviews what fires. Sentinel ships Microsoft connectors and analytics rule templates you can use as a starting point, and its playbooks run on Azure Logic Apps, which Microsoft bills separately. Splunk positions Enterprise Security Premier as bringing SIEM, user behavior analytics, SOAR and AI together, while its SOAR page says SOAR used with Enterprise Security requires a Splunk SOAR subscription, so check which automation your quote includes.

Which fits a small team?

Illustrative situations, not client stories:

• A 50-person Microsoft 365 firm whose auditor wants a year of logs. Sentinel: Office 365 audit logs and Defender alerts are free to ingest, and older data can move to the cheaper lake tier.
• A company with Splunk already deployed and staff who know it. Keep Splunk; moving detection rules and dashboards to another platform takes time you could spend tuning.
• A network built largely on Cisco equipment. Splunk's half-weight counting of eligible Cisco telemetry may change the math; get a quote that shows it.
• No regulator or insurer asking for logs. Neither yet. Start with XDR and someone watching it.
• A SIEM is required but nobody can run one. A managed SOC that operates the SIEM for you, with the sources and retention written into the agreement.

What affects cost, implementation and support?

• Volume. Daily gigabytes of paid sources; chatty firewalls and verbose server audit policies drive it.
• Retention. Sentinel includes the first 90 days and charges for longer; on Splunk, retention is part of the quote.
• Licenses you already own. Free Defender alerts on Sentinel, and the E5 data grant if you qualify.
• People. Rule tuning and alert review, in-house or managed, continue every month after setup, so budget for them as a running cost, not a project.
• Platform changes. Sentinel users on the Azure portal need to move to the Defender portal by March 31, 2027.

How does NetSys help?

Disclosure first: NetSys deploys Microsoft Sentinel for clients whose compliance obligations call for a SIEM, and where one is not justified we say so and cover the environment with Defender XDR instead. Our SOC monitoring service scopes the work before quoting: which sources connect and what each costs to ingest, retention, coverage hours, severity definitions and who we call, and which containment actions we may take without waiting. Source health is checked, because a log source that stops reporting is a blind spot, not a quiet night.

Book a call with a NetSys engineer to estimate your daily log volume and how much of it Sentinel would ingest free.

Frequently asked questions

Is Microsoft Sentinel cheaper than Splunk?

Sentinel is easier to price, because Microsoft publishes per-GB rates and several Microsoft sources are free to ingest. Splunk publishes no Enterprise Security prices, so the comparison needs a quote for your volume, retention and pricing model.

What is the difference between Microsoft Sentinel and SentinelOne?

Microsoft Sentinel is a SIEM that collects and correlates logs. SentinelOne is a separate company that sells endpoint protection and XDR, plus its own SIEM. A business can run SentinelOne on its devices and send that data to Microsoft Sentinel.

Is Azure Sentinel the same as Microsoft Sentinel?

Yes. Azure Sentinel is the earlier name of the same product, which Microsoft now calls Microsoft Sentinel and is moving into the Microsoft Defender portal.

What affects cost, implementation and support?

Daily data volume, retention, the licenses you already own and the people who tune rules and review alerts. Implementation is connecting and testing each source; support is the ongoing review, in-house or through a managed SOC.

Does a small business need Splunk?

Usually not as a first purchase. A small business without a regulator asking for logs gets more from XDR watched by a managed service; one that needs central logs and runs on Microsoft 365 will find Sentinel simpler to start.