For one, you can export to CSS, LESS, SASS and Stylus. I think Parfait only exports to CSS.
We cannot speak for the Parfait team, but we think there are some key differentiators given that their tool is from Adobe. Read Q11 at http://avocode.com/faq.html
I know Sketch is mentioned in the FAQ as something that may come later. But, Sketch is quickly becoming the darling of the web design world, and the development world just hasn't adopted it yet. Want to corner the market? Support Sketch sooner, rather than later. I'm really looking forward to seeing what Avocode can do!