Short answer: Testsigma is the right choice when you want one platform to hold your entire QA practice — web, mobile, API, test management and reporting. Testmode is the right choice when you want tests running this afternoon without adopting a platform.

Both let you write tests in something close to plain English, so the usual comparison — natural language versus code — does not apply here. The real differences are how the sentence becomes an action, and how much of your process the tool expects to own.

At a glance

	Testsigma	Testmode
Test authoring	Natural-language steps from a structured grammar	Free-form plain English
How a step is resolved	Mapped to a defined action, with element locators	An AI agent interprets intent at run time
Scope	Web, mobile, API, plus test management	Web applications
Setup	Platform onboarding, project and suite configuration	Point it at a URL
Best suited to	An established QA team standardising on one tool	Teams with little or no automation today
Cost model	Commercial, with an open source edition	Commercial product

Where Testsigma is the better tool

You need mobile and API coverage in the same tool. Testmode tests web applications. If native mobile is a first-class requirement, that is a real gap and Testsigma covers it.
You want test management, not just test execution. Test cases, plans, requirements traceability and reporting in one system matters to regulated and larger QA organisations.
You have a dedicated QA team. Testsigma rewards a team that will invest in learning it properly and standardise on it.
You want the option of self-hosting. There is an open source edition.

Where Testmode fits better

You want to skip the platform adoption. Testsigma is a system you roll out. Testmode is a URL and a sentence. For a team without an existing QA practice, that difference is most of the decision.
You want free-form description, not a step grammar. Structured natural-language steps are still a syntax to learn — they constrain what you can say so the platform can resolve it reliably. Testmode takes the sentence as written and lets the AI work out how to carry it out.
Your application changes constantly. Locator-based resolution, even self-healing, is anchored to how the page was built. Interpreting intent at run time degrades more gracefully through a redesign.
The tester is not in QA at all. If the person writing the test is a product manager, a founder or an operations lead, a full QA platform is more tool than the job needs.

The honest summary

Testsigma is the broader product. If you need mobile, APIs and test management under one roof and you have the team to run it, it will do more than Testmode does.

Testmode is narrower on purpose. It does web application testing, driven by an AI that reads your sentence and figures out the rest. If your alternative today is manual testing or nothing, the shortest path to a working test matters more than breadth.