301 or 302 Redirects to Mobile Site

[SEOTGT]

When it's detected that a mobile device is accessing the site it has the ability to redirect from www.example.com to m.example.com. Does it make more sense to employ a 301 or 302 redirect here?

Google says a 301 but does not explain why (although usually I stick to "when in doubt, 301") . It seems like a 302 would prevent passing link juice to the mobile site and having mobile-optimized results also showing up in Google's index. What is the preference here?

[BrianJGomez]

Thanks for sharing that link. That's interesting that Google is telling you to create a 301 for desktop to mobile redirects. I've always used this script and it's worked great never negatively impacted my Mobile or Desktop SERPS: