Ask HN: Develop productivity app first for Mac or Windows 10?

I want to create a productivity app, which runs in the background, and reminds me to work on my most important tasks, when it thinks that I am not. The goal is to create a Minimal Viable Product which I, and others, find useful. Which of the two platforms has more potential customers? In other words: What is the market share of Mac vs Windows 10 among people who happily try out new productivity apps? My coding skills: I am an experienced backend developer, but have not done a Mac or Windows 10 app yet. I like both OS.

1000 thanks for any thoughts or hints.