Both of these put the form inside a WordPress site you already run, so responses stay in your own database and no one is counting your submissions. They differ on who they think is holding the mouse.
What each one optimises for
WPForms optimises for the first hour. The editor and the template set are built so that somebody who has never made a form gets to a working one quickly, and a free version in the plugin directory means the first form costs nothing. The price of that is a licence ladder: conditional logic and calculations are not in the free version, and the integrations are spread across four annual tiers at regular prices of $99, $199, $399 and $599 a year.
Gravity Forms assumes more of you and gives more back at the bottom. There is no free version at all — the entry licence is $59 a year for a single site — but conditional logic, calculations, file uploads and a save-and-continue link are core rather than tier-gated. Payments, signatures and the richer connections arrive as add-ons whose availability depends on the licence, and a REST API covers anything the interface does not.
Both handle payments without taking a cut on an active licence, though WPForms applies a three percent platform fee to payments made through the free version.
How the money actually works
Compare the second year, not the first. WPForms promotional pricing is routinely about half the renewal, so a licence bought at $49.50 renews near $99. Gravity Forms publishes a renewal price that matches the purchase price, and sale periods discount the first year in the same way. On a single site with logic and calculations required, the entry Gravity licence is the cheaper standing cost.
Which should you choose?
Choose WPForms if you are building the form yourself and are not comfortable in WordPress. It is genuinely easier at the start, the free version will carry a contact form indefinitely, and the guided editor is worth the tier you will eventually buy.
Choose Gravity Forms if the form has real work to do — calculations, long applications, save-and-continue, an API. Everything that matters is in the entry licence, and you will not discover halfway through building that the feature you need is two tiers up.

Gravity Forms
No free version, no response limits, and an annual licence for your own site.

WPForms
A beginner-facing WordPress plugin with a free version and four licence tiers.
Specs
Ratings
Ease of building
How the form looks
How much you can change it
Logic and question types
What happens after submit
Value for money
Features
Pricing
Gravity Forms
WPForms