figma is pretty freaken amazing, and it works outside of macs. So overall there is nothing but upsides to it. Collaboration is amazing too. Just... No down sides.
They have an API using which you get a json representation of your files. That is the same as sketch (whose file format is essentially zipped json files).
I could switch to Figma from Sketch very easily because I could upload my Sketch files in Figma and Figma could deconstruct them into layers and elements with even layer names intact!
Vice versa? No.
Even Photoshop files .PSD are readable in many other photo editing apps.
Figma is significantly more expensive than Sketch, e.g. for individuals: $144/year vs ($99 for first year + $79 for next years), and that's if you choose to upgrade Sketch every year, which you don't need to.
Figma have a free plan which works perfectly fine for my purposes (implementing designs given to me by designers, and very occasionally making my own).
