While Facebook has redrawn and shares these assets for the benefit of the design community, Facebook does not own any of the underlying product or user interface designs. By accessing these assets, you agree to obtain all necessary permissions from the underlying rights holders and/or adhere to any applicable brand use guidelines before using them. Facebook disclaims all express or implied warranties with respect to these assets, including non-infringement of intellectual property rights.
Feel free to use these files in any private or public space. Please do not repackage and redistribute these as your own.
Illustrator is still highly relevant for its strength, vector based work, while Sketch has surpassed Photoshop for UI.
The momentum is only increasing, even with bugs and issues found in Sketch. It's obvious the interface design community desires better tools. I wonder if Adobe Comet stands a chance with disruption we're seeing?
Alternatively, you could take that money and rent either Illustrator for 3 months or all of Creative Cloud for 2 months.
Even if I didn't like Sketch better, that would be tough to argue with.
SVG, OpenDocument, ... are real XML based formats.
I suppose this would also go for Flux/React/GraphQL and, to a lesser extent, Open Compute.