Google's John Mueller said on Twitter that they treat hreflang found in your XML Sitemaps file and HTML code markup equally. We know it is more efficient and manageable for larger sites to use Sitemaps for hreflang. But either way - they both provide the same level and weight of signals to Google.
Of course, you want to make sure not to have them conflict with each other. We know this topic is one of the more complex SEO topics out there right now.
Here are the tweets:
sure
— John ☆.o(≧▽≦)o.☆ (@JohnMu) June 12, 2018
They are even processed at the same time as crawling:
No, processing would be at the same time as with on-page annotations (assuming we've seen the sitemap beforehand, which is the general case).
— John ☆.o(≧▽≦)o.☆ (@JohnMu) June 12, 2018
Forum discussion at Twitter.
