Best practice is best practice. Header redirects are messy, confusing, easily forgotten about, and decrease your SEO/rank to the nth degree. They should only be used as a very short-term redirect hack while you're working on a live site and need a temporary redirect elsewhere.
You might not care about your blog's rank, but it's always a good idea to use the most professional solution so that it becomes second nature to you, rather than falling back on outdated procedures. If you decide it's not worth your time to move the blog folder contents into the domain root, implement an .htaccess permanent redirect instead - web spiders will then treat domain.com/blog as being the 'official' domain.com landing page.
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