Should I get Developer or Business Support Plan for learning AWS?

For learning AWS, the Developer Support plan would be more appropriate than Business Support.

The Developer Support plan is designed for experimentation and testing scenarios, which aligns well with learning purposes. It provides access to technical support with response times of up to 24 hours for general guidance questions and up to 12 hours for system impairment issues.

The Developer plan includes benefits like best practice guidance, building-block architecture support, and an unlimited number of support cases. You'll also get access to AWS Trusted Advisor, the AWS Support API, and client-side diagnostic tools.

Business Support is more expensive and designed for production workloads with faster response times (up to 1 hour for production system down). If you're primarily learning and not running critical production systems, the additional cost of Business Support may not be justified.

While AWS re:Post is a community-driven question-and-answer service that's available to all AWS customers, your experience with response quality may vary. A Developer Support plan would give you direct access to AWS technical support engineers who can help with your specific learning questions.
Sources
AWS Support Plans
AWS Support Resources - Amazon Web Services
AWS Support Plans - AWS Support
Creating support cases and case management - AWS Support