When to use deepseek flash and pro?

Hey, Most of the time I'm building web apps either with flask or django, yet I don't have knowledge in building UI so I'll be using AI to demonstrate my work, also using it to trouble shoot issues, right now I'm on linux and using aider and deepseek in the CLI to navigate my projects (also if you know a better workflow tell me about it), and wanted to know when to choose between flash and pro.