A migration review should begin with the routes that can cause immediate loss. Design differences matter later if search engines cannot reach, interpret or transfer value to the new pages.
Confirm the redirect map
Test old URLs in bulk. Each important route should reach the closest relevant new page in one step. Redirect chains, loops and broad redirects to the homepage hide the real mapping problem.
Compare index controls
Review robots rules, noindex tags, canonical URLs, hreflang and XML sitemaps. A staging rule or copied canonical can remove large sections from consideration.
Check page equivalence
A redirect does not preserve intent when the new page drops the content, product or service the old page represented. Compare headings, main copy, internal links and structured information.
Review internal discovery
Important pages should still receive links from navigation, categories, related content and other relevant pages. A valid URL can lose visibility when the new structure buries it.
Use several data sources
Server logs, crawl data, Search Console, analytics and rank tracking answer different questions. Compare them by page group rather than looking only at the total site line.
Once critical controls are stable, move to slower issues such as content quality, template differences and conversion behaviour. The first task is to make sure the intended site can be found and understood.