Image Re-Crawling Takes Longer After a URL Change
Images are not crawled very frequently, so when you migrate them to new URLs/domains, it will take a lot longer than pages, perhaps months.
Wildcard Subdomain Configuration Causes Crawl Issues
Using wildcard subdomains can make a site difficult to crawl.
CSS and JS Crawling Is Important for Mobile Compatability
Noindex Pages Can’t Accumulate PageRank
Noindex pages can’t accumulate pagerank for the site, even though the pages can be crawled. So this isn’t an advantage over disallowing.
Disallowed URLs Don’t Pass PageRank
If a URL is disallowed in robots.txt, it won’t be crawled, and therefore can’t pass any pagerank.