Which PGDM specialisation should I opt marketing or operations? What are the salary prospects if I opt operation management?

Marketing has good salaries and prospects for roles senior sales position. On the contrary, operations have fewer jobs and decent enough salaries in 4-8 LPA range.

Go for operations management specialisation if you already have an engineering degree with Production Engineering. For marketing, you can go for consumer behaviour, strategic marketing management, brand management, brand equity, etc. and also supply chain and retail management.