Difference between robots.txt and sitemaps index file

Question

Do I need a sitemap index file if I have multiple sitemaps?

At the moment I just specify multiple sitemaps in my robots.txt, is the equal to having the index file?

Answer 1

Technically yes, but it isn't the most efficient - for several reasons:

1. Multiple instructions as opposed to one
2. Inability to assign priority or freshness (using timestamps)
3. Requires more manual maintenance when updating/changing both the robots.txt file and Google/Bing webmaster tools etc