I just went through this with some of my sites. Some of my URLs were showing up in searches with HTTP URLs, while others were showing up with HTTPS URLs. Digging deeper also showed both HTTP and HTTPS being indexed.

This isn't an HTTPS preference on Google's part. It's (effectively) a mis-configuration on the web site operator's part.

HttpWatch (and many other folks with web sites) should either be using 301 Redirects or, in many cases where that's not compatible with other things being done, using the Canonical link element to indicate with https content is just a copy of http content.

So: Try setting your ‘canonical’ line properly in your web pages. Then this won’t happen.

Right now HttpWatch's http pages report their http as canonical. Their https pages report https as canonical. They effectively are listing their site twice with Google (and probably splitting/hurting SEO, but that's another story.)

https://support.google.com/webmasters/answer/139066?hl=en

http://en.wikipedia.org/wiki/Canonical_link_element

http://googlewebmastercentral.blogspot.com/2013/04/5-common-...

http://www.mattcutts.com/blog/canonical-link-tag/