diff b/w Change Sets vs. Eclipse.

 Via eclipse you can do deployment but there will not be any track that which classes or pages are deplyed previously.

1. If you use change set all the old deployments will be tracked.
2. Change set can be cloned.

  So Change set will be better option :)

diff b/w validate and deploy changeset in salesforce

Validate Changeset: This step will validate your Changeset component and will also check for the Test coverage (75%). After validation you can deploy the changeset or you can keep it without deployment.

Deploy Changeset is superset of Validate Changeset beacuse if you directly click on Deploy Changeset, it will first perform Validation and on successful validation of Changeset component it will deploy those component.