Difference Between Views and Tables in Performance

It depends.

As long as the View does not contain aggregations (or constructs that require materialisation 'upfront'), it will be exactly the same performance (and in many cases can pass through where criteria with shortcircuiting by the optimiser)

Have you tried benchmarking in your specific cases?

@Otávio Décio beat me to it, by mentioning that having the 'correct' indexes will have a greater effect on performance.

Performance is a lot more dependent on having the appropriate indexes than if you are using a view or direct table access, which (except for materialized views) behave exactly the same way.

When you use select count(*) from view it will significantly slow than table. Because the table contains row number on its header, a view doesn't have such information.