[open-source-ux]

Both would work well assuming you are using them for UI design. Note that Sketch is Mac only though. Although Figma runs in the browser, they also have Electron-based desktop apps for Mac and Windows.

Purchasing Sketch gives you one year of updates. If you decide not to renew the subscription, the app is still yours to keep and run - but you won't get any new updates. Figma follows the SaaS model of subscription, but they do have a free tier.

Sketch also has a lot more tutorials and plugins than Figma at the moment, in case that is important.